Editing History of Boos

'''[[Boo]]s''' are among the more commonly appearing enemy species of the [[Super Mario (franchise)|''Super Mario'' franchise]]. Though they first appear in ''[[Super Mario Bros. 3]]'', Boos most prominently appear in the [[Luigi's Mansion (series)|''Luigi's Mansion'' series]]. In spinoff series, Boos have had a variety of roles, such as being an item in the [[Mario Kart (series)|''Mario Kart'' series]] or obstacles in certain minigames of the [[Mario Party (series)|''Mario Party'' series]]. Sometimes, a Boo has appeared as a playable character, such as in the [[Mario Tennis (series)|''Mario Tennis'' series]], and the [[Nintendo 64]] version of ''[[Mario Tennis (Nintendo 64)|Mario Tennis]]'' is the first time a Boo was made a playable character.
==''Super Mario'' series==
===''Super Mario Bros. 3'' / ''Super Mario Advance 4: Super Mario Bros. 3''===
[[File:SMB3Boo.jpg|thumb|left|Artwork of a "Boo" Diddly from ''Super Mario Bros. 3'']]
Boos first appear in ''[[Super Mario Bros. 3]]'' and return in its [[Super Mario Advance 4: Super Mario Bros. 3|Game Boy Advance version]]. Here, they are referred to as "Boo" Diddlys, a pun on the name of the late rockstar {{wp|Bo Diddley}}. However, future games refer to them only as Boos. They make their first appearance in {{world-link|2|fort|World 2-Fortress}}. The "Boo" Diddly shields its face if [[Mario]] or [[Luigi]] looks at it, but it starts to chase Mario or Luigi, faster than in succeeding games, if they look away. "Boo" Diddlys are unable to be defeated unless the two are equipped with a [[Hammer Suit]], [[Green Shell|Koopa shell]], or [[Super Star|Starman]]. The game also has [[Stretch]]es, which are "Boo" Diddlys with very long bodies that live in the fortresses throughout the [[Mushroom World]]. In the original, depending on the level's palette, "Boo" Diddlys have either a dark-blue or dark-red outline.

===''Super Mario World'' / ''Super Mario World: Super Mario Advance 2''===
[[File:SMWBoo.png|frame]]
In ''[[Super Mario World]]'' and its enhanced port ''[[Super Mario World: Super Mario Advance 2]]'', "Boo" Diddlys are now called "Boo" Buddies (though they were still called "Boo" Diddlys earlier in development<ref>{{cite|title=[[tcrf:Prerelease:Super Mario World (SNES)/Background Graphics and Tilemaps#Enemy Cast List|Prerelease:''Super Mario World'' (SNES)/Background Graphics and Tilemaps § Enemy Cast List]]|publisher=The Cutting Room Floor|accessdate=August 6, 2020}}</ref>) and they reside in the many [[Ghost House]]s in the game. These "Boo" Buddies retain their usual pattern of attack from ''Super Mario Bros. 3'' and sometimes make faces at Mario or Luigi. However, they are somewhat slower and less accurate than in ''Super Mario Bros. 3''. This game also introduces many new "Boo" Buddy variations, such as the [[Block Boo|Boo Buddy Block]], [[Boo Buddy Snake]], [[Boo Crew]], [[Boo Buddies|Circling Boo Buddies]], [[Eerie]]s, and [[Disappearing Boo Buddy|Disappearing Boo Buddies]]. It also introduces a giant version of the "Boo" Buddy, the [[Big Boo]]. One Ghost House contains a secret boss, a special [[Big Boo]]. The only way to defeat a "Boo" Buddy is with [[Super Star]]s or with [[Grab Block]]s when it is visible. Unlike later games, the "Boo" Buddies in this game seem to have multiple tails. The groups of "Boo" Buddies also have different facial expressions, while individual "Boo" Buddies change theirs for a brief second if they are stared at long enough.

===''Super Mario Land 2: 6 Golden Coins''===
[[File:SML2 Boo.png|frame|left]]
Boos appear in ''[[Super Mario Land 2: 6 Golden Coins]]''. Compared to other games, they move in a slower, wave-like pattern toward Mario. Boos in this game are found in the [[Pumpkin Zone]]. A thrown [[Green Shell]] can defeat it. A variant named [[Ghost Goomba]]s also appears in this game.

===''Super Mario 64'' / ''Super Mario 64 DS''===
{{quote|Ghosts...don't...DIE! Heh, heh, heh! Can you get out of here...alive?|Message from Big Boo's Haunt}}
[[File:Boo 64.png|thumb|120px|left|A Boo in ''Super Mario 64'']]
[[File:SM64DS BigBoo.png|thumb|175px|A Boo in ''Super Mario 64 DS'']]
Boos (also called '''Baby Boos''')<ref>{{cite|author=Prima Bath|date=April 7, 1999|publisher=[[Prima Games]]|isbn=0-7615-2103-8|title=''Nintendo 64 Game Secrets, 1999 Edition'' Prima's Official Strategy Guide|page=84-87}}</ref> make a starring appearance in the course [[Big Boo's Haunt]] in ''[[Super Mario 64]]''. A group of Boos can be found in the [[Peach's Castle|Mushroom Castle]]'s [[courtyard (Peach's Castle)|courtyard]] (eight of which are holding [[Red Coin]]s in the DS version). After collecting twelve [[Power Star]]s, Mario is able to enter Big Boo's Haunt by going into the little cage (also called a "carousel")<ref>{{cite|author=Pelland, Scott and Dan Owsen|title=''Super Mario 64'' Player's Guide|page=48}}</ref> that a Big Boo drops. He also battles an extra-large [[Big Boo (character)|Big Boo]] three times here. Additionally, when Mario looks at the Boos, they attempt to hide by becoming partially transparent, but if Mario is not looking at them, they chase him. If they hit him, he loses two wedges of [[Health Meter|health]]. In the translucent Boo, the player can see a [[coin|Yellow Coin]] or a [[Blue Coin]]. Boos can be defeated from a punch or kick either from behind or the side. A Boo can also be defeated from a [[Ground Pound|Pound the Ground]] attack while Mario is not looking at them. When defeated, they give a Blue Coin, but the ones in the courtyard give a normal coin instead. When a Boo is defeated in the first mission, [[Go on a Ghost Hunt]], it says, "''Ghosts...don't...DIE! Heh, heh, heh! Can you get out of here...alive?''" In addition, a Boo appears in the hallway of the Mushroom Castle after twelve Stars are collected.

In ''[[Super Mario 64 DS]]'', Boos use their current design introduced in ''Mario Party 4''. Additionally, eight Stars are needed to spawn a small Boo in the hallway, who holds a Red Coin. After fifteen Stars are collected, the small Boo is replaced by a Big Boo, which then allows Mario, Luigi, or Wario to enter Big Boo's Haunt. If the [[Eye to Eye in the Secret Room|sixth mission]] is selected and the player is not Luigi, one particular Boo wears [[Luigi Cap|Luigi's cap]]. In the haunt, Mario can find a Luigi [[painting]], which takes him to the [[Big Boo Battle]] level on the balcony. After defeating [[King Boo]] within, Mario gains the key to the room in which Luigi is imprisoned and proceeds to free him. In the English version of the game, King Boo is also referred to as "Big Boo," resulting in three separate entities with that name. Yoshi cannot defeat Boos in this game. Ground-pounding yields no results, and eating them simply causes Yoshi to spit them back out. Boos that end up being eaten will say, "''You...can't...EAT...ghosts! Eee hee hee!''" Mario, Luigi, or Wario can hit them with Pound the Ground attacks. Additionally, Luigi can also use the [[Spin Jump|spin jump]] from his [[Backward Somersault|backward somersault]] to defeat Boos.

===''Super Mario Bros. Deluxe''===
{{multiframe|[[File:Super Mario Bros Deluxe Boo.png]] [[File:SMBDX Green Boo.png]] [[File:SMBD Redboo.png]] [[File:BlackBoo.png]]|The Boos from<br>''Super Mario Bros. Deluxe'',<br>arranged by speed}}
While Boos do not appear in the original ''[[Super Mario Bros.]]'', Boos appear in ''[[Super Mario Bros. Deluxe]]'' as competitor characters in the "You VS. Boo" mode. The goal is to reach the [[Goal Pole|flagpole]] before the Boo. After defeating Boo within a certain time frame, it flies away, and a green Boo replaces it. After that Boo is defeated, a red Boo takes its place, and finally, a '''Black Boo'''<ref>{{cite|language=en-us|title=''Super Mario Bros. Deluxe'' instruction booklet|page=20|publisher=Nintendo of America|author=Nintendo|date=1999}}</ref> with a yellow outline appears. Each new Boo gets progressively faster than the one before it, meaning the plain White Boo is the slowest, while the Black Boo is the fastest; the Black Boo copies the player's best time, which makes it the hardest to defeat. Unlike other games, these Boos do not hurt the player on contact.

===''Super Mario Sunshine''===
[[File:SMS Boo Artwork.jpg|thumb|left|100px|A Boo from ''[[Super Mario Sunshine]]'']]
Boos return in ''[[Super Mario Sunshine]]'', terrorizing the residents of [[Hotel Delfino]]. In this game, they move around in slow, swooping motions and do not care if Mario looks at them. They tend to go in Mario's general direction while turning invisible (aside from some distortion), but spraying them with [[F.L.U.D.D.|FLUDD]] causes them to slowly become visible again. These Boos can be defeated by being jumped on, making ''Super Mario Sunshine'' the only game outside of the ''Super Mario'' RPGs where jumping can defeat them. Boos in this game can also be eaten by Yoshi. They also disguise themselves as [[Yellow Coin]]s and [[Blue Coin]]s, which only spin to face Mario instead of spinning at a constant pace. Boos can also disguise themselves as [[Shadow Mario]] while the real Shadow Mario runs from Mario, though they appear lighter than Shadow Mario, lack the [[magic brush]], and do not have the theme music. When Mario approaches a disguised Boo, it laughs and bumps into him, though if it is sprayed beforehand it will start behaving like the other Boos. Like the other returning enemies, Boo's design is changed for this game, with drooping eyelids, blue circles surrounding their black pupils, and long, coiled tails. This is due to the fact that they are made from [[goop]].<ref>{{cite|title=''[[Encyclopedia Super Mario Bros.|Encyclopedia Super Mario Bros]]''|page=107}}<!--Do not add quote, since this is coming from a book that is commercially available.--></ref>

The Boos in this game are led by [[Big Boo (character)|King Boo]]. Mario finds him in the basement of the hotel's Casino, and he has to battle him. He can defeat him by throwing a [[Chili Pepper]] at him and then throwing another piece of [[fruit]] at him. Mario has to do this three times before King Boo is defeated. [[Block Boo|Pink Boo]]s also appear and can be turned into a platform if sprayed by FLUDD. Also appearing inside the hotel are a new species, known as [[Sleepy Boo]]s. These large Boos mostly appear to block passages. FLUDD's water does not affect them; they can be removed only by being eaten by [[Yoshi]].

===''New Super Mario Bros.''===
[[File:NSMBDS Boo Sprite.gif|frame|right]]
Boos also appear in ''[[New Super Mario Bros.]]'' They are found mainly in Ghost Houses scattered throughout the game, as well as [[World 8-1 (New Super Mario Bros.)|World 8-1]]. They appear like they usually do, shy, and they act the same as in ''Super Mario Bros. 3''. They can only be defeated with a [[Shell]], a [[Super Star|Starman]], a [[Mega Mushroom]], or a [[Blue Shell]]. The game also introduces the [[Balloon Boo]], which are normal Boos who can suck up air, and become much bigger. [[Broozer]], the boxing ghost, first appears in this game as well. An icon of 2 Boos covers the progress map in Ghost Houses.

===''Super Mario Galaxy''===
[[File:Mario Seek.png|thumb|left|Mario looking at a Boo in ''Super Mario Galaxy'']]
Boos make an appearance in ''[[Super Mario Galaxy]]'' and can be found in the [[Ghostly Galaxy]], the [[Bigmouth Galaxy]], the [[Deep Dark Galaxy]], and the [[Sand Spiral Galaxy]]. Boos act the same way that they did in previous games, such as hiding by turning transparent when Mario looks at them and then following Mario when he looks away. Boos can be defeated only when they are brought under a ray of light (including the Toad Brigade captain's helmet and the light emitted from shells while in the water) or by [[Rainbow Mario]] touching them. The spin attack, however, can throw a Boo around Mario, knocking it off course temporarily or into a light. Boos can also be found underwater in the [[Bigmouth Galaxy]] where they attack just by swimming back and forth, similar to [[Cheep Cheep]]s. In [[Deep Dark Galaxy]], in the secret mission, there is a large Boo that has a [[Power Star]] in it. 

[[Boo Mario]] also appears in this game. Mario has the same body as the other Boos, but retains his face when in his Boo form. He also wears his trademark cap on his head. If a Boo spots Mario while he is a Boo, it develops an attraction for him and follows him. If a Boo hits Mario, Mario loses the power-up but does not lose any health.

An [[Big Boo|Atomic Boo]] makes an appearance in this game, as well as a racing one named the [[Spooky Speedster]]. This game also introduces a new kind of Boo, called the [[Bomb Boo]]; it is similar to a normal Boo, but it is black with yellow eyes and can be grabbed by its tongue if Mario uses his spin attack on it.

[[Captain Toad]] also indirectly suggests that Boos eat people, as he worried that Luigi might have been eaten by ghosts.

===''New Super Mario Bros. Wii''===
[[File:NSMBW World 3-GH Screenshot.png|thumb|A Boo chasing Mario in ''New Super Mario Bros. Wii'']]
Boos reappear in ''[[New Super Mario Bros. Wii]]'' in Ghost Houses throughout the game. They behave the same way as they did in ''New Super Mario Bros.'' and are invincible, unless the player has a [[Super Star|Star]] power-up. [[Big Boo]]s also reappear along with [[Broozer]]s. [[Boo Buddies|Circling Boo Buddies]] can also be found in a small number of Ghost Houses in the game. Despite their concept art, they appear with a blue glow as opposed to plain white in this game, giving off a more spectral appearance. In the level selection screen, a single Boo will be watching Mario and will taunt Mario as he enters. If Mario gets tossed out, the Boo will laugh. However, once the level is beaten, the Boo will cover its face for the rest of the game.

===''Super Mario Galaxy 2''===
[[File:SMG2 Boo Moon Graveyard Planet.png|thumb|left|Boos in the [[Boo Moon Galaxy]] in ''Super Mario Galaxy 2'']]
Boos reappear in the game ''[[Super Mario Galaxy 2]]''. They behave the same way they did in its predecessor. They are found in haunted levels such as [[Haunty Halls Galaxy]] and [[Boo Moon Galaxy]]. The underwater Boos from the predecessor also appear in this game, in the [[Battle Belt Galaxy]] and [[Slimy Spring Galaxy]]. [[Bomb Boo]]s also reappear. As well, two new variants have been introduced: [[Octoboo]]s, which resemble ghostly [[Octoomba]]s; and [[Mega Boo]]s, which are larger than [[Big Boo]]s.

===''Super Mario 3D Land''===
Boos later appear in ''[[Super Mario 3D Land]]''. In the game, they retain their normal battle strategy, which is chasing [[Mario]] when he looks away while sticking their tongue out. Boos in this game also momentarily disappear when hit with [[Fire Mario]]'s fireballs and [[Tanooki Mario]]'s tail whips. Boos also laugh in their original phonic from ''[[Super Mario 64]]''. Some Boos have [[Raccoon Mario|striped tail]]s; these are called [[Tail Boo]]s. They act like normal Boos, but when they stop moving when Mario looks at them, they will swing their tails once, which can damage Mario. Big Boos also appear during the game. Another species of Boo is also introduced, called [[Peepa]]s. They do not move freely like normal Boos and instead move around a set position, and do not halt when Mario looks at them, as in ''[[Super Mario Galaxy]]''.

===''New Super Mario Bros. 2''===
Boos, along with [[Big Boo]]s, return in ''[[New Super Mario Bros. 2]]'', with the same appearance and behavior as in ''New Super Mario Bros. Wii'', except they turn completely red when Mario faces them. They can be found in Ghost Houses along with other ghost enemies such as [[Peepa]]s and the new [[Boohemoth]]. All of these varieties, save for Boohemoth, can be defeated with a Star or [[Gold Flower]]. Boos can also be turned [[Gold Boo]]s with a [[Gold Ring]]. When gold, Boos float away from Mario, leaving a trail of coins behind them.

There are also Boos that push walls in a Ghost House, namely World 4's [[World 4-Ghost House (New Super Mario Bros. 2)|Ghost House]]. Here they push the wall either left or right and they do not stop when Mario looks at them.

===''New Super Mario Bros. U''===
[[File:BooNSMBU.png|thumb|Artwork from ''New Super Mario Bros. U'']]
Boos, [[Big Boo]]s, and [[Boo Buddies|Circling Boo Buddies]] appear in the [[Wii U]] title ''[[New Super Mario Bros. U]]''. Their behavior is the same as that of past installments. Boos also have their own [[Enemy Course]] in the [[Soda Jungle#Haunted Area|haunted area]] of [[Soda Jungle]], where a group of Boos appear in an area with various [[Donut Block]]s, and defeating them must be done using the [[Super Star]] located inside a [[Flying ? Block]]. They can also be defeated with a [[Baby Yoshi]].

===''Super Mario 3D World'' / ''Super Mario 3D World + Bowser's Fury''===
Boos appear in ''[[Super Mario 3D World]]'' and its [[Nintendo Switch]] port ''[[Super Mario 3D World + Bowser's Fury]]'', along with [[Peepa|Peepas]] and [[Big Boos]]. They retain the same strategy from ''Super Mario 3D Land'' and utter the same laugh from ''Super Mario 64''. They appear to be a bit more transparent than in previous mainstream ''Super Mario'' games and give out a blueish glow like in the ''New Super Mario Bros.'' games, as well as a reddish glow and even steam when Mario faces them.

===''Super Mario Maker'' subseries ===
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Boos reappear in ''[[Super Mario Maker]]'', ''[[Super Mario Maker for Nintendo 3DS]]'', and ''[[Super Mario Maker 2]]'' as enemies. They function the same as previous games. They have been given new sprites for the ''[[Super Mario Bros.]]'' style. In the Course Maker, they can be placed as enemies and can be shaken to turn into [[Boo Buddies]]. They can also be dragged onto a platform, turning them into [[Stretch]]es. Like many enemies, they can be enlarged by a [[Super Mushroom]] and be given wings. The former will turn it into a Big Boo, and the latter will make them move much faster. They can be placed in [[Warp Pipe]]s, [[Bill Blaster]]s, [[Block]]s, and [[track]]s. In addition, adding Wings to a Boo Buddy makes the Boo Buddy move in and out. If a Boo is placed in a [[Koopa Clown Car]], the Koopa Clown Car stops and closes its eyes when it is looked at, and sneaks up on the player when looking away.

===''Super Mario Run''===
[[File:SMRBoo.png|frame|right]]
Boos appear in ''[[Super Mario Run]]'' in Ghost House levels. When Mario looks at them, they cover their eyes and float up and down. They attack Mario by quickly following behind him. Mario can defeat them by jumping over them while they are giving chase by using a [[Backflip Block]] or a [[Wall Jump]]. In some levels, pressing the pink [[P Switch]] defeats Boos on-screen. They can drop [[Key]]s, [[Coin]]s, or [[Color coin]]s after they are defeated, and the object they contain inside of them can slightly be seen through them before they are defeated. In [[Dark and Stormy]], Boos are defeated when a lightning strike occurs. Stretches also appear in the game.
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===''Super Mario Bros. Wonder''===
[[File:SMBWKingBoo.png|thumb|King Boo with several other Boos in ''Super Mario Bros. Wonder'']]
Boos reappear as enemies in ''[[Super Mario Bros. Wonder]]''. Here, they look similar to their older 2D artwork, although they still stick their tongues out. Boos behave the same way as in other games, and can be defeated by luring them into light like in the 3D ''Super Mario'' games. Additionally, [[King Boo]] returns during a [[Wonder Effect]].
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==DIC cartoons==
===''The Adventures of Super Mario Bros. 3''===
[[File:CartoonBoo.jpg|thumb|A Boo in ''The Adventures of Super Mario Bros. 3'' episode "[[Reign Storm]]".]]
Boos make infrequent appearances in ''[[The Adventures of Super Mario Bros. 3]]'' television series, which depicts them as having a somewhat menacing appearance. They are depicted with red eyes and yellow teeth. Like in the game the show is based on, Boos work for Bowser and often aid him in causing trouble. An example of this is seen in the episode "[[Reign Storm]]," in which Bowser has several Boos terrorize the new Mushroom Shopping Mall. In this episode, they are referred to as "Boo Diddlys."

===''Super Mario World'' television series===
[[File:SMWTV Yoshi and Boo.jpg|thumb|left|Yoshi encountering a Boo in the ''Super Mario World'' television series episode "[[The Night Before Cave Christmas]]".]]
In ''[[Super Mario World (television series)|Super Mario World]]'', Boos, who are completely redesigned, appear in the episodes "[[Ghosts 'R' Us]]," in which a gang of Boos, as well as a Big Boo, appears to chase [[Yoshi]] through [[Wizenheimer]]'s haunted house; "[[The Night Before Cave Christmas]]," in which they scare Yoshi away; and "[[The Yoshi Shuffle]]," in which several Boos appear in the audience during the episode. They are never referred to by name, instead simply being referred to as "ghosts". They more closely resemble their in-game sprite.
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==''Nintendo Adventure Books''==
[[File:Capers.jpg|thumb|Boos chasing Luigi on the front cover of ''[[Koopa Capers]]'', the fourth of the ''Nintendo Adventure Books'']]
In ''[[Koopa Capers]]'', a Boo confronts Luigi if he decides to simply look through a keyhole in a fortress door, instead of barging through it. If Luigi decides to run away from it immediately, he will successfully escape, but if he decides to stand his ground, the Boo will chase him onto some floating blocks after he dodges its attack. Making a beeline for the door after mounting the blocks will allow the Boo to catch Luigi, but doing evasive techniques will allow him to escape it. When he begins his descent into the Magma Pit, Luigi will hear a Boo behind him, which causes him to pick up the pace, and escape it.

Illustrations of a Boo are used in puzzles in ''[[Dinosaur Dilemma]]'' and ''[[Flown the Koopa]]'', though none appear in the actual stories.

==''Super Mario World: Mario to Yoshi no Bōken Land''==
[[File:SMWM&YALBoos.png|thumb|left|Boos swarming Luigi, Yoshi, and Mario from ''Super Mario World: Mario to Yoshi no Bōken Land'']]
In the interactive OVA ''[[Super Mario World: Mario to Yoshi no Bōken Land]]'', Boos appear in a [[Ghost House]] that [[Mario]], [[Luigi]], and [[Yoshi]] are passing through. A Boo starts following Luigi, who is in the back, but every time he turns around, it disappears. Finally, he quickly does a double take, and turns just in time to see it re-materialize. He panics and Boos start swarming the group. Mario grabs a candle and lights it, which repels the Boos, and one drops a key they need to progress.
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==''Yoshi'' franchise==
===''Yoshi''===
[[File:BooY.jpg|thumb|100px|A Boo Buddy from ''Yoshi'']]
Boo Buddies make an appearance as one of the six falling objects in ''[[Yoshi (game)|Yoshi]]''. Boo Buddy's sprite in this game is similar to its sprite from ''[[Super Mario World]]''.

===''Yoshi's Cookie''===
In ''[[Yoshi's Cookie]]'', Boos return as enemies to [[Yoshi]]. Though in this game, they are depicted as one of Yoshi's "opponents". They are among the easy opponents, the others being [[Goomba]], [[Cheep Cheep]], [[Koopa Paratroopa|Paratroopa]], and [[Spiny]]. [[Eerie]]s also appear, as well as the similarly-named [[Fishing Boo|Fishin' Boo]]s. 

===''Yoshi's Safari''===
[[File:YoshiSafariBoo65.png|thumb|left|A Big Boo from ''Yoshi's Safari'']]
Boos<ref>{{cite|title=''Yoshi no Road Hunting'' instruction booklet|language=ja|date=1993|publisher=Nintendo|author=Nintendo|page=21}}</ref> (misnamed "Big Boo" in the English manual<ref>{{cite|title=''Yoshi's Safari'' instruction booklet|page=20|language=en-us|author=Nintendo|publisher=Nintendo of America|date=1993}}</ref>) are enemies in ''[[Yoshi's Safari]]'', where they are encountered only in [[Ghost Mansion]]. Unlike most enemies in the game that can be shot with the [[Super Scope]] to be defeated, shooting a Boo stops it in its tracks. While stunned, [[Yoshi]] can then run into it to defeat it. Defeating a Boo adds 500 points to the player's score (1,000 in Hard Mode), the highest amount of points earned from regular enemies. A [[Big Boo]] serves as the boss for the level.
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===''Yoshi's Island'' series===
[[File:Bigger Boo SMW2YI Artwork.png|thumb|200px|Boos in ''[[Super Mario World 2: Yoshi's Island]]'' have smaller eyes and thinner eyebrows compared to its contemporary depictions, as well as bottom fangs. This design is later used in the first three installments in the ''[[Paper Mario (series)|Paper Mario]]'' series.]]
In ''[[Super Mario World 2: Yoshi's Island]]'' and its [[Yoshi's Island: Super Mario Advance 3|enhanced Game Boy Advance port]], Boos first appear in [[World 2 (Super Mario World 2: Yoshi's Island)|World 2]], alongside several other ghastly creatures. They can be defeated only by looking away and then making an [[Yoshi's Egg|egg]] bounce off of a wall after it is thrown, hitting the ghost in the face. [[Kamek]] the [[Magikoopa]] turns one Big Boo into [[Bigger Boo]], which serves as a mini boss and grows in size every time he is hit by an egg. The main boss of World 2 is also a Boo-like creature, [[Roger the Potted Ghost]], who was a normal flower pot until Kamek made him giant and transformed it into a living creature. The game also features the [[Boo Balloon]], who are balloons made to look like Boos that yield items when they pop, as well as [[Blindfold Boo|Boo Man Bluff]], a blindfolded Boo that relies on noise to detect the player.

Boos appear in both sequels, ''[[Yoshi's Island DS]]'' and ''[[Yoshi's New Island]]'', behaving identically as in ''Super Mario World 2: Yoshi's Island'' and being able to be defeated in the same way as before. In ''Yoshi's Island DS'', there is also a Boo-like midboss in [[Hector the Reflector]]. Boos in ''Yoshi's New Island'' first appear in [[Beware the Boo Brigade]] and retain their laugh from ''Super Mario 64''.

===''Yoshi's Story''===
[[File:Yoshis Story Boo.png|thumb|120px|left|A Boo in ''Yoshi's Story'']]
Boos appear in ''[[Yoshi's Story]]'' in Stage 6-3: [[Ghost Castle]]. They do not act differently, although they are slightly bigger. The Ghost Castle is also home to other Boo species: namely, the [[Block Boo]], [[Blindfold Boo]], and [[Mini Boo|Little Boo]]s. Another variant, the [[Jelly Ghost]], inhabits the [[jelly]] of Stage 2-3: [[Jelly Pipe]] and Stage 2-4: [[Torrential Maze]]. The [[Big & Little Boo]] family also appears in Jelly Pipe.

The normal Boo<ref>{{cite|quote=[[Media:Yoshi Story Shogakukan P7.jpg|「ヨッシーストーリー 任天堂公式ガイドブック」]]|title=''Yoshi's Story Nintendo Kōshiki Guidebook''|page=7|language=ja|publisher=[[Shogakukan]]}}</ref> is mistakenly called a Big Boo<ref>{{cite|author=Leung, Jason; Munson, Terry; Pelland, Scott|title=''Yoshi's Story'' Player's Guide|publisher=Nintendo Power|page=10|date=1998|language=en-us}}</ref> in the ''[[Nintendo Power]]'' guide.

===''Yoshi Topsy-Turvy''===
Boos in ''[[Yoshi Topsy-Turvy]]'' only appear in mission 6-7, with Big Boos being more common. They follow the same tactics as normal, and are given their laugh from preceding releases.
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==''Mario Kart'' series==
===''Super Mario Kart''===
{{multiframe
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Boos made their first appearance in the ''[[Mario Kart (series)|Mario Kart]]'' series in ''[[Super Mario Kart]]'' as items exclusive to "2 Player" mode, under the name "'''Ghosts'''".<ref>{{cite|date=1992|publisher=Nintendo|author=Nintendo|title=''Super Mario Kart'' instruction booklet|page=14}}</ref> When the player uses it, they will become transparent temporarily (19 seconds), while the "Ghost" steals the opposing player's item, if available. They also appear as background elements in [[SNES Ghost Valley 1|the three]] [[SNES Ghost Valley 2|Ghost Valley]] [[Ghost Valley 3|courses]], where they laugh when the player drives by.

===''Mario Kart 64''===
[[File:BooMK64.png|frame|left]]
Boos (named '''Ghost Bonuses''' on one occasion<ref>{{cite|title=''Nintendo Magazine System'' (AU) Issue 49|date=April 1997|page={{file link|NMS Australia 49 MK64 drivers and items.jpg|39}}}}</ref>) return as a usable item in ''[[Mario Kart 64]]''. They can be obtained if the player is in the top two positions. When activated, the Boo selects a racer with the best item in reach, steals the item, and gives it to the player that released it. At the same time, the player obtains total invisibility and invincibility for a short period of time. While invisible, the player can pass the items, the course obstacles, and the other racers more easily by simply going through them. If no other players possess items, the Boo will return empty-handed. Boos also appear in [[N64 Banshee Boardwalk|Banshee Boardwalk]] and the image of one appears in neon lights in [[N64 Rainbow Road|Rainbow Road]], both as background elements.

===''Mario Kart: Super Circuit''===
[[File:MKSC Boo Alternate Artwork.jpg|thumb|A Boo from ''Mario Kart: Super Circuit'']]
Boos appear as items again in ''[[Mario Kart: Super Circuit]]''. When activated, they can also slow down the leading racer. Starting in this game, if a CPU racer uses a Boo, it can also steal items from the player and make the player lose Coins. The transparency effect lasts for five seconds.

Boos, also referred to as "ghosts",<ref>{{cite|author=Walsh, Doug|date=August 21, 2001|isbn=0-7440-0091-2|title=''Mario Kart: Super Circuit'' Official Racing Guide|publisher=BradyGames|page=92}}</ref> also appear in two new courses, [[GBA Boo Lake|Boo Lake]] and [[Broken Pier]]. At Boo Lake, Boos hold candles that guide the player through the track. On Broken Pier, they attack the players and take their [[Coin]]s.

===''Mario Kart: Double Dash!!''===
Boos do not appear as items in ''[[Mario Kart: Double Dash!!]]''. However, Boos, as well as the Boolossus' gold frame portrait, appear in the [[GCN Luigi's Mansion|Luigi's Mansion]] battle course. Also, King Boo makes his ''Mario Kart'' debut as a playable character alongside his partner, [[Petey Piranha]].
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===''Mario Kart Arcade GP'' subseries===
[[File:MKAGPDX Boo.png|thumb|120px|left|Boo item from ''Mario Kart Arcade GP DX'']]
Boos appear as items in the arcade game, ''[[Mario Kart Arcade GP]]''. A Boo appears as a basic item. It causes whoever is hit by it to slow down temporarily. There is also a new item called the '''Triple Boo'''. Boos reappear in ''[[Mario Kart Arcade GP 2]]'' and ''[[Mario Kart Arcade GP DX]]'', functioning identically as before.
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===''Mario Kart DS''===
[[File:MKDS Boo Sprite.png|thumb|Boo item from ''Mario Kart DS'']]
Boos, named '''Boo Hoo''' in the European instruction manual<ref>{{cite|title=''Mario Kart DS'' European English instruction manual|url=cdn02.nintendo-europe.com/media/downloads/games_8/emanuals/nintendo_ds_21/Manual_NintendoDS_MarioKartDS_EN.pdf|format=PDF|date=2005|language=en-gb|page=12}}</ref>, return as items in ''[[Mario Kart DS]]''. They can be obtained if the player is anywhere from 3rd to 7th place. This time, they no longer slow down the leading racer, nor do they steal the best item in reach. Instead, they just steal the nearest racer's item. However, while using the Boo item in this game, the player will not be slowed down while driving on off-road surfaces, allowing various shortcuts to be made. Some pictures of Boos from the game, ''[[Luigi's Mansion]]'', appear in the [[DS Luigi's Mansion|Luigi's Mansion]] race course. {{classic-link|N64|Banshee Boardwalk}} reappears as a race, along with the Boos. They do not do anything that affects the racer; they just laugh when a racer drives by.

===''Mario Kart Wii''===
Much like in ''Mario Kart: Double Dash!!'', Boos do not appear as items in ''[[Mario Kart Wii]]'', but [[King Boo]] appears as a playable character. However, Boos do appear in a returning course, {{classic-link|SNES|Ghost Valley 2}}. Like their original appearance in the track, Boos only laugh when racers drive by, but they eventually disappear. Boo also makes a cameo in Bowser's Castle. At the end of the track, Boo's ''Mario Party 7'' artwork can be seen along with Dry Bones' artwork.

===''Mario Kart 7''===
In ''[[Mario Kart 7]]'', Boos appear in the returning track, [[DS Luigi's Mansion|Luigi's Mansion]], in place of the portrait ghosts. They will pop out of their paintings when the drivers race by them. They also appear as spectators on [[3DS Toad Circuit|Toad Circuit]] and {{classic-link|N64|Luigi Raceway}}.

===''Mario Kart 8'' / ''Mario Kart 8 Deluxe''===
[[File:Hammer Knight MK8D.jpg|thumb|A Boo inside a Hammer Knight from ''Mario Kart 8'']]
[[File:MK8D Luigi and Boo Item Screenshot.png|thumb|left|Luigi holding a Boo from ''Mario Kart 8 Deluxe'']]
In ''[[Mario Kart 8]]'' and ''[[Mario Kart 8 Deluxe]]'', Boos appear as obstacles in [[Twisted Mansion]]. If aimed correctly, the players can land on the Boos floating around near the gliding section. They also possess [[Hammer Knight]]s near the end of the track. These same Boos can also be seen floating around on {{classic-link|GCN|Luigi's Mansion}} in ''Mario Kart 8 Deluxe'' and {{classic-link|GBA|Boo Lake}} in the ''[[Mario Kart 8 Deluxe – Booster Course Pass]]'', the latter where they replace the candle Boos from the original iteration.
 
''Mario Kart 8 Deluxe'' reintroduces Boos as items. Boos immediately steal an item from a random racer in front of the user, and invincible or other invisible players are not immune; the Boo will bring back a Mushroom if there is nothing to steal. The Boo is visible, both when it steals an item and when it gives the stolen item to the user. It takes a couple more seconds to deliver the item back to the user, however. Only one Boo can be in play at a time; once it brings back an item, another can appear in [[Item Box]]es again, even while another player is still invisible. Due to the way deployed items work, a Boo is able to steal any timed or multiple usage item, except for a [[Crazy Eight]], [[Piranha Plant]], or [[Bullet Bill]] already in use. Stealing such an item will always give the user a fresh version of the item.<ref>{{cite|author=Mankalor|date=May 8, 2017|title=Mario Kart 8 Deluxe Tips - Boo Item Analysis|url=youtu.be/OUdaqb7Cj2I|publisher=YouTube|accessdate=May 9, 2017}}</ref> Unlike ''Mario Kart DS'', the player can no longer cut through off-road sections while invisible.

[[King Boo]] also returns as a playable character in ''Mario Kart 8 Deluxe''.
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===''Mario Kart Tour''===
[[File:MKT Boo Wooden Cutout.png|thumb|A wooden cutout of two Boos in ''Mario Kart Tour'']]
Boos reappear in ''[[Mario Kart Tour]]'' in the courses [[SNES Ghost Valley 1]], [[SNES Ghost Valley 2]], [[GBA Boo Lake]], [[DS Luigi's Mansion]], and [[RMX Ghost Valley 1]], where they act the same as they did on those courses in previous games. [[Wooden cutout]]s of Boos also appear in the Ghost Valley courses and DS Luigi's Mansion.

In every [[Halloween Tour]] since 2020, the [[Autumn Tour (2021)|2021 Autumn Tour]] and the [[Battle Tour]], [[Jack-o'-lantern]]s are scattered throughout the courses, some of which had Boo faces. Additionally, King Boo is once again a playable character. A glider known as the [[Boo Masks]] also appears in the game as [[Princess Peach|Peach (Yukata)]]'s signature glider, who also has a Boo ribbon.

===''Mario Kart Live: Home Circuit''===
Boos reappear in ''[[Mario Kart Live: Home Circuit]]'' in [[Boo Fortress]], frightening racers who hit them.
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==''Super Mario Adventures''==
In ''[[Super Mario Adventures]]'', a horde of Boos appear to attack Mario and Luigi when they are tricked into a haunted house by Bowser and the [[Koopalings]]. Mario and Luigi become trapped by the Boos and a Big Boo, who are held at bay by the bros staring at them in the face. Eventually, nearing exhaustion, Mario races to a nearby room, dragging Luigi while being chased by the Boos. Upon barging into this room, the Boos and Big Boo find Mario [[Dr. Mario|dressed as a psychiatrist]] with Luigi as his nurse. After some talking, Mario and Luigi manage to reform the Boos and the Big Boo, while learning they were bullied in their youth (which is why they act so nasty to everyone). These Boos and their Big Boo leader were last seen happily waving goodbye to Mario, Luigi and Yoshi as they left the haunted house, which the Boos led them out of.

Boos also make an appearance at [[Princess Peach|Toadstool]]'s wedding.
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==''Super Mario Bros.'' film==
While Boos do not physically appear in the 1993 [[Super Mario Bros. (film)|''Super Mario Bros.'' film]], a [[:File:VoteKoopaFilm.png|sign saying "NOW PLAYING BOO DIDLEY"]]{{sic}} can be seen in [[Dinohattan]].

==''Mario Bros.'' series==
===''Mario Bros.''===
[[File:MBSNES Boo.png|frame|left]]
Boos make an appearance in the ''[[Super Mario All-Stars]]'' remake of ''[[Mario Bros. (game)|Mario Bros.]]'', where they replace the [[Fireball (obstacle)|fireball]]s in the [[Battle Game (Super Mario All-Stars)|Battle Game]] found in the main menu of ''[[Super Mario Bros. 3]]''.
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===''Mario Clash''===
[[File:Big Boo Artwork - Mario Clash.png|thumb|Artwork of a Big Boo from ''Mario Clash'']]
Boos<ref>{{cite|title=マリオクラッシュ (''Mario Kurasshu'') instruction booklet|page=20|date=1995|author=Nintendo|publisher=Nintendo|language=ja}}</ref> (misnamed "Big Boo" in the English manual<ref name=ClashBoo>{{cite|title=''Mario Clash'' instruction booklet|page=21|date=1995|publisher=Nintendo of America|language=en-us|author=Nintendo}}</ref>) make appearances in the [[Virtual Boy]] game, ''[[Mario Clash]]'', where they are among the target enemies. In this game, Mario is able to attack a Boo from the side. Boos can become transparent by becoming dark like the screen, which causes them to become invulnerable, with [[Koopa Shell|shell]]s simply passing through. For some reason, the English manual also refers to the Boos using feminine pronouns, similar to [[Cheep Cheep]] in the original ''[[Super Mario Bros.]]''<ref name=ClashBoo/>

==''Hotel Mario''==
[[File:HM Boo.png|thumb|left|A Boo from ''Hotel Mario'']]
Boos also appear in the game ''[[Hotel Mario]]'' under the name '''Boo Buddies'''.<ref>{{cite|title=''Hotel Mario'' instruction book|page=16|date=1994}}</ref> Some Boos behave similarly as in the ''Super Mario'' series: attacking Mario when his back is turned and hiding behind their arms when looked at. However, while Mario is in an elevator, these Boos wander in diagonal patterns. There are some other Boos that are normally transparent and wander in a similar manner, regardless of where Mario looks, but occasionally become fully visible and quickly charge at him.
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==''Mario's Picross''==
Boos in ''[[Mario's Picross]]'' appear in one of the pictures in the "Early Picross" stage in level 6C. The other character that appears in the "Early Picross" stage is [[Mario]], who appears in level 6H. Like their first appearance, ''[[Super Mario Bros. 3]]'', they appear under the name '''Boo Diddly'''.
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==''Super Mario RPG: Legend of the Seven Stars''==
[[File:SMRPG Big Boo Artwork.png|thumb|Artwork of a Boo from ''Super Mario RPG: Legend of the Seven Stars'']]
Boos return during the events of ''[[Super Mario RPG: Legend of the Seven Stars]]'' and its [[Super Mario RPG (Nintendo Switch)|Nintendo Switch remake]]. In the original game, the English translation erroneously calls them "The Big Boo", whereas the remake simply calls them Boos. In the Japanese version, they are, in fact, referred to as Teresa as they are in other games. These Boos, like other Boos that appear in previous games, hide behind their arms when stared at. However, some Boos teleport around the room, attempting to scare Mario and his friends. Boos live in [[Kero Sewers]] along with many other ghouls, including [[Hobgoblin]]s and [[Shadow]]s. Often, these three undead monsters will assist each other in battle. Boos have no physical defense, making them extremely weak enemies (for reference, a [[Goomba]] is the weakest enemy encountered and it has three defense points). However, Boos make up for their lack of defense with high evasion, meaning that most attacks against Boos will miss. In battle, Boos command powerful lightning magic, including the attacks [[Lightning Orb]] and [[Bolt (move)|Bolt]]. Boos also know the special attack [[Scream]], which cuts a party member's [[fear|attack and defense in half]]. When not using magic, Boos approach one of Mario's party members and make a face, damaging that character. In this game, there is also a stronger Boo variation called [[High Boo]]s, which are the same size as their normal counterparts but have blue tongues, similar to the first appearance of [[King Boo]]. The only true appearance of a Big Boo in this game is the one used in [[Bowser]]'s [[Terrorize]] attack.<ref>{{cite|title=''Super Mario RPG: Legend of the Seven Stars'' English instruction booklet|page=41}}</ref> One Boo lives in [[Monstro Town]] as part of the [[Three Musty Fears]].

==''Super Mario-kun''==
[[File:Boo SuperMarioKun 8.jpg|thumb|left|Boo as it appears in ''Super Mario-kun'']]
Boos make appearances in some of the ''[[Super Mario-kun]]'' comics. A Boo appears on the cover of the sixteenth issue. This issue is based on ''[[Super Mario 64]]''. Alongside it, [[Eyerok]], a [[Bob-omb]], and [[Bowser]] can be seen. Throughout the comic, they appear, too. Their role in the comic is similar to their role in the game, where they are enemies to Mario and attempt to attack him. [[Lady Bow]], a notable Boo, appears in a couple of the ''[[Paper Mario]]''-based issues. These issues are 25 and 27. Lady Bow appears on the cover of the twenty-fifth issue along with many of [[Mario]]'s other partners, including [[Goombario]], [[Kooper]], [[Eldstar]], and [[Twink]]. Besides appearing on the cover, she appears throughout the comic. Her role in the comic mimics her role in the game. Lady Bow reappears on the cover of the twenty-seventh issue and in the comic. Like in issue 25, Lady Bow's role in the comic is similar to her appearance in the game, where she helps Mario. In a ''[[Super Mario Galaxy]]''-based issue, [[Boo Mario]] appears on the cover along with more of Mario's transformations.
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==''Game & Watch Gallery'' series==
===''Game & Watch Gallery 2''===
Boos (called "Boo Buddies") appear in the Modern version of ''[[Vermin]]'' in ''[[Game & Watch Gallery 2]]''. When [[Yoshi]] looks in the general direction of them, they refuse to move. When Yoshi looks away, they move towards the eggs. They only appear in groups of two or just one.

===''Game & Watch Gallery 4''===
[[File:G&WG4BooSprite.png|frame]]
A Boo appears in the Modern versions of ''[[Donkey Kong 3 (Game & Watch)|Donkey Kong 3]]'', ''[[Mario's Cement Factory]]'', and ''[[Boxing]]'' in ''[[Game & Watch Gallery 4]]''. In ''Donkey Kong 3'', if Mario or Donkey Kong turns his back, it will slowly come closer to the player that it is closer to. If it gets close enough, the Boo will either scare Donkey Kong and award the player points (single-player mode only) or scare Mario and give the player a miss. In ''Mario's Cement Factory'', a Boo will fly into the two containers on the second floor, clogging them up. The player does not receive any points for removing the Boo. In ''Boxing'', one of the opponents [[Luigi]] faces is a [[Big Boo]], who uses a regular Boo as a boxing glove.
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==''Mario Party'' series==
Boo has been a major character in the ''Mario Party'' series, from being a thief for hire to being a playable character.
===''Mario Party''===
[[File:CrazyCutter.png|thumb|left|Players cutting out Boos in Crazy Cutter from ''Mario Party'']]
Boos make minor appearances in ''[[Mario Party]]''. Their voices can be mimicked by one of the items: the [[Talking Parrot]]. Boos also appear in each of the game's board maps, excluding [[Peach's Birthday Cake]]. On the boards, they steal [[Coin]]s or [[Star (Mario Party series)|Stars]] from opponents, and they are willing to steal a few coins for free from any player, although they will steal the number of coins at random. They also ask for 50 coins to steal a Star. If the player tells Boo that they do not want to steal anything, Boo will say "''Don't feel so guilty. Ha ha ha!''" Additionally, after the Luigi's Engine Room board is completed, a Boo, [[Koopa Troopa|Koopa]], and a [[Toad]], along with the two runner-ups, surround the victor and congratulate them. Boos also appear in several mini-games, including [[Pedal Power]] and [[Running of the Bulb]], and as one of the shapes the player can cut in the minigame, [[Crazy Cutters|Crazy Cutter]].

===''Mario Party 2''===
Boos make several appearances in ''[[Mario Party 2]]''. In it, they steal Coins or Stars as they did in the first game. However, Boo charges 5 coins to steal coins instead of a free steal; and steals much more than in the first game. Additionally, an item called the [[Boo Bell]] appears. When a player obtains it, they can ring for a Boo to come. The Boo that comes to the player's side is asked to steal Coins or Stars, depending on how much the player can afford. If the Boo is sent to steal Coins from an opponent, the opponent can fight it off by pressing the A button quickly. Additionally, the Boo can only steal a maximum of 30 coins or a maximum of one Star.

A Boo also appears in the battle minigame [[Day at the Races]] along with the other racers; [[Whomp]], [[Thwomp]], and [[Bob-omb]]. The Boo can disappear and then reappear in a further spot on the racetrack. However, it gets its face stuck in the ground sometimes, causing it to stop for a short period of time. In [[Skateboard Scamper]], the players must use their skateboards to escape a pursuing Boo.

===''Mario Party 3''===
[[File:CurtainCallMP3.png|thumb|Boos in [[Curtain Call]] from ''Mario Party 3'']]
Boos also appear in ''[[Mario Party 3]]''. Like in their previous appearances, they are not major characters in the game. They are among the Duel Partners in the [[Mario Party 3#Duel Mode Partners|Duel Mode Partners]]. It is [[Yoshi]]'s default partner, and when an opponent attacks, Boo can counterattack for equal damage, unless it is defeated by a [[Thwomp]]. Boo will only counterattack a [[Chain Chomp]] if it is directly in front of the Chomp when it attacks. Boo's attack is two, its stamina is one, and its salary is three coins.

Boos also appear in the unlockable party board, [[Waluigi's Island]]. Whenever a player runs into a Boo, it shows them two paths. One of the paths is rigged. If the player chooses the rigged path, they are sent back to the start. If they choose the correct path, they continue on the board. In addition, Boos appear on all of the other boards, [[Chilly Waters]], [[Deep Bloober Sea]], [[Spiny Desert]], [[Woody Woods]], and [[Creepy Cavern]], serving the same function as in the previous games. On the board map, a picture of them can be seen next to a grave. They also return with the Boo Bell. Boos are also in the minigames [[Curtain Call]], [[Stacked Deck]], [[Three Door Monty]], and [[Crowd Cover]]. Two portraits of a Boo can also be seen in [[Locked Out]].

===''Mario Party 4''===
[[File: Booparty4.jpg|thumb|x200px|left|The sorcerer Boo from ''Mario Party 4'']]
In ''[[Mario Party 4]]'', a Boo plays a major role as the host for [[Boo's Haunted Bash]]. This is the first game where Boos use their modern design. This Boo wears a wizard's hat and cape, and like the other hosts in the game, it is the character to reward the player with a Star. Multiple Boos also appear on this board as background characters. A particularly surly one controls the Item Shop. Another one owns the [[Mystery Train]], but it only gives out rides to the Boneyard if a [[Red Boo]] is not in its presence. Two side games involving Boos require a [[Mini Mushroom]]. One of them has the player pressing one of the keys of the Horn of Plenty to get one of three randomly chosen items. The second one has the character on a piano. They have to press the correct key at the right time until the end of the side game to get a certain amount of Coins. A question mark space activates a Boo clock. If three people land on them, Big Boo will appear. Big Boo is basically an upgraded version of the Boo House; it targets all players instead of one. The caped Boo is also the fourth host of the Reversal of Fortune, who oversees what is given.

Boos also appear on every other board in the game, stealing coins and Stars for the player at a shop called the [[Ghost House#Mario Party series|Boo House]] in the same manner as Boos' previous appearances in the ''Mario Party'' series.

Also, a Boo is an unlockable, playable character in the Extra minigame, [[Beach Volley Folley]].

In [[Long Claw of the Law]], a Boo is one of the possible characters that needs to be collected.

===''Mario Party 5''===
In ''[[Mario Party 5]]'', Boo is a playable character in Party Mode, and it is one of the newcomer playable characters, the others being [[Koopa Kid]] and [[Toad]]. Boo's partner in the game is [[Koopa Kid]]. Since Boo is playable, it does not make any major background appearances. Its previous role on the boards is now fulfilled by [[Chain Chomp]].

===''Mario Party 6''===
A Boo reappears as a playable character in ''[[Mario Party 6]]''. In the game, there is also an orb called [[Boo Away Orb]], which protects the player from a [[Red Boo]]. Red Boos also appear in the minigame [[Boo'd Off the Stage]] and [[Boonanza!]]. Red Boos also appear on two boards, [[Towering Treetop]] and [[Castaway Bay]] where they let players steal coins and stars from others at night, similar to the Boo House in ''Mario Party 4''. This game also marks the third appearance of Red Boos in the ''Mario Party'' series.

===''Mario Party Advance''===
{{quote|Ee hee hee! It's ghastly news!|Boo|Mario Party Advance}} 
[[File:MPA Mr E Horror Condo.png|thumb|Boos in the [[Horror Condo]] in ''Mario Party Advance'']]
Boos appear in ''[[Mario Party Advance]]'' as supporting characters. Four of them haunt [[Boo Cemetery]], although one of them is soon revealed to be an impostor. As a part of their mission, [[True-Blue Boo]], the player is asked to identify and reveal the impostor along with their [[golden Boo statue]] in exchange for the [[Predictotron]].

When the player visits the cemetery, they are greeted by the four Boos. They mention a crime when [[Shroomlock]] appears to assist them. At the mention of a theft, the Boos become worried and ask them to help track down their golden Boo statue, which they consider a symbol of their friendship. At this time, they appear to realize there are four Boos rather than their usual three, assuming one of them is an impostor. The player is asked to select the Boo with a slightly different moveset and rhythm, revealed to be [[Koopa Kid]] if correct. Although he gets away, the statue is left behind. As thanks for this, the remaining Boos award the player the Predictotron. According to the information preceding the credits, the Boos now regularly haunt [[Horror Condo]].

Boos also appear in a few minigames, including [[Boo-Bye]]. In this minigame, regular Boos appear alongside Red Boos and Blue Boos. They also appear in [[Spooky Spike]], in which one Boo serves volleyballs to the player, [[Floor It!]], in which Boos are one of the possible passengers that must be brought to their respective floor, and [[Porta-Gust]], in which the player can suck up Boos into a vacuum.

===''Mario Party 7''===
''[[Mario Party 7]]'' marks the third ''Mario Party'' game where Boo is playable. It also marks [[Dry Bones]]' first playable appearance, who is Boo's partner throughout the game. Red Boos appear in the game, too. Red Boos appear in a few minigames such as [[Ghost in the Hall]]. In this minigame, Red Boos try to scare the players. Oddly, the Red Boos also try to scare Boo, if Boo is one of the characters. Boo shares the same special orb with Dry Bones, the [[Magic Orb]]. It allows them to double their dice roll during the next two turns and turns them invisible, making them immune to traps.

===''Mario Party 8''===
[[File:BooMP8Official.png|thumb|Boo from ''Mario Party 8'']]
In ''[[Mario Party 8]]'', Boo is a playable character for the fourth time in the ''Mario Party'' series. Boo's partner is Dry Bones, again. Red Boos appear in some minigames such as [[Boo-ting Gallery]]. ''Mario Party 8'' also marks the first appearance of [[King Boo]], who is the board host of [[King Boo's Haunted Hideaway]]. In order to get a Star, the player must find the room King Boo is hiding in and give him ten coins. There are three rooms, two of which contain a trap hole. If the player finds one of these rooms, several Red Boos will throw them in, forcing the player to start back at the beginning. When the player gets a Star, King Boo will rearrange the mansion's rooms. Red Boos appear as owners of the item shops.

===''Mario Party DS''===
Boo is not a playable character in ''[[Mario Party DS]]'' and plays no part in board play, but appears as an unlockable figure. They also appear in the minigames [[Boo Tag]], and [[Peek-a-Boo (minigame)|Peek-a-Boo]]. In Boo Tag, a Boo tags a player. The tagged player must try to get rid of the Boo by running into another player. The player that spent the least amount of time with the Boo wins. In Peek-a-Boo, the players must find the wanted Boo. A lot of different Boos appear in hats and different colors such as red, blue, green and yellow. Several of the wanted Boo appear, and once they are all gone, the game is over. The team that won the most Boos wins.

===''Mario Party 9''===
Boo does not return as a playable character in ''[[Mario Party 9]]'', however [[King Boo]] is the boss of [[Boo's Horror Castle]]. Normal Boos also appear on the board. When the player passes a Boo portrait, a Boo will emerge and chase after the player. These Boos will move three spaces after each turn, and if a Boo catches up to the players (or vice versa), the current captain will lose half of all of their [[Mini Star]]s.

During [[King Boo's Puzzle Attack]], whenever King Boo's health is depleted halfway, he sends Boos to attack the player. If the player's cursor touches a Boo, they are temporarily stunned. King Boo only sends one Boo at a time.
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===''Mario Party: Island Tour''===
[[File:Boo Artwork (alt) - Mario Party Island Tour.png|thumb|Boo from ''Mario Party: Island Tour'']]
Boo returns as a playable character in ''[[Mario Party: Island Tour]]''. This is the fifth time that Boo is playable, the first time it is playable on a handheld ''Mario Party'' game, and it is the first character in the series to be removed as a playable character in a main installment of the series and then return in a later installment.

===''Mario Party 10''===
[[File:King Boo's Tricky Tiles MP10.png|thumb|left|Boss minigame [[King Boo's Tricky Tiles]] from ''Mario Party 10'']]
Boo reappears in ''[[Mario Party 10]]'' as a non-playable character. Whenever the player reaches [[Boo (area)|a certain spot]] in the board [[Haunted Trail]], Boo appears and steals five Mini Stars from a specific player for an indefinite number of turns. Boo will continue to harass the player until passed off to another player via a [[Boo Space]] or driven towards a [[Streetlight]]. Boos also appear in the minigame [[Boo Burglars]], as enemies the players must examine, and appear as a balloon in the minigame [[Balloon Blast Bash]]. Several Boos also make cameos in the [[Luigi Board]].
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===''Mario Party: Star Rush''===
[[File:Boo'sBlockParty amiibo.jpg|thumb|Boo's Block Party from ''Mario Party: Star Rush'']]
In ''[[Mario Party: Star Rush]]'' Boo has a special mode called Boo's Block Party. Players can participate in a single-player endless mode for a high score or compete in a one-on-one versus mode. When a player uses the Boo [[amiibo]] in Boo's Block Party, four Boos appear in the background: two on the top screen and two on the Touch Screen. If a player taps the Boo amiibo in the Mario Shuffle mode, the player can use Boo in that mode. They also appear in the [[Haunted Hallways]] and [[House of Boos]] minigames.

===''Mario Party: The Top 100''===
In ''[[Mario Party: The Top 100]]'', Boo appears in minigames such as [[Slot Trot]] from ''Mario Party 6'' and [[Jigsaw Jumble]] from ''Mario Party 9''. However, in Minigame Match, Boo appears as an item via [[Boo Bell]].

===''Super Mario Party''===
Boo returns as a playable character in ''[[Super Mario Party]]'', which is its sixth playable appearance in the ''Mario Party'' series. Because of its status as a playable character, [[Lakitu]] takes its role as the one who steals coins or Stars from the earlier ''Mario Party'' installments. Its Boo Dice Block consists of two of each -2 coins, 5, and 7.

===''Mario Party Superstars''===
Boo returns as a non-playable character in ''[[Mario Party Superstars]]'', behaving like it does in the first three ''Mario Party'' games. Boos also return in [[Roll Call (minigame)|Roll Call]] and [[Crazy Cutters]].

==''Mario Golf'' series==
{{MGTT character infobox
|title=Boo
|image=[[File:ToadstoolTour Boo Mug.png]]
|drive=208 yards
|star_drive=253 yards
|trajectory=Slice
|height=3/5
|impact=13/21
|star_impact=09/21
|control=10/21
|spin=08/21
}}
Boos make a couple of appearances in the ''[[Mario Golf (series)|Mario Golf]]'' series. In ''[[Mario Golf (Nintendo 64)|Mario Golf]]'' and in ''[[Mario Golf: Toadstool Tour]]'' a Boo appears in the top right corner of the screen to indicate the speed and direction of the wind.
===''Mario Golf''===
In ''[[Mario Golf]]'' for the [[Nintendo 64]], Boos show where the wind blows by facing its direction in relation to the camera angle. They do not appear if there is no wind. Hole 2 of [[Mario's Star (golf course)|Mario's Star]] is designed after Boos. Also, Boos appear in the artwork for one of the courses, [[Boo Valley]]. Boo's name appears on the scorecard sometimes.

===''Mario Golf: Toadstool Tour''===
Boo is one of the unlockable characters in ''[[Mario Golf: Toadstool Tour]]'', the others being [[Bowser Jr.]], [[Shadow Mario]], and [[Petey Piranha]]; it is the only one to have not debuted in ''Super Mario Sunshine'' and is the only one that appears in the opening clip. In [[Bowser Badlands]], Boos affect the trajectory of balls hit through them. Boos once again reprise their role of showing the wind direction, but they have another role; if a player delays in starting their swing, then two Boos carry a sign and float across the screen. These signs describe basic gameplay tips, but some are taunts to the player.

===''Mario Golf: World Tour''===
[[File:BooHoleInOne.jpg|thumb|left|Boo getting a [[Hole-in-One]] in ''Mario Golf: World Tour'']]
Boo returns in ''[[Mario Golf: World Tour]]'' as a playable character, this time being available from the start. Boos also appear in Hole 4 of [[Bowser's Castle (golf course)|Bowser's Castle]] floating in the sky alongside [[King Boo]]. For this installment, a "blowing cloud" is used instead of a Boo to indicate wind speed and direction.

===''Mario Golf: Super Rush''===
A Boo appears as a Spin character in ''[[Mario Golf: Super Rush]]'', where the standard version is available normally and a version with a visor available as an unlockable for playing in Ranked Match. Boo has the highest Spin stat in the game. Boo's Special Shot is Mischief Twister, in which multiple Boos appear and merge into Boo's golf ball before the swing for the shot is made. If it lands near other balls, Boos will come out and haunt them. Balls that are haunted cause the trajectory in the shot gauge to be curved, resulting in the shot not being able to travel in a straight line unless a special shot is used. Boo's Special Dash is the Carousel Dash, which causes multiple Boos to circle around Boo and carry Boo forward. Because Boo levitates, they are not penalized by travelling across any body of water or lava, although travelling on them will deplete the stamina gauge, and if it fully depletes, the character will travel back to the surface before contacting water or lava (this trait is shared with [[Rosalina]]).

In Golf Adventure mode, Boo appears as part of the rookie class with the player’s Mii, Toadette, and Chargin’ Chuck.

==''Mario Tennis'' series==
===''Mario Tennis''===
[[File:Mt64boo.png|thumb|Boo from ''Mario Tennis'' (Nintendo 64)]]
Boo is a default character in the [[Nintendo 64]] version of ''[[Mario Tennis (Nintendo 64)|Mario Tennis]]'', his first playable appearance. He is classified as a tricky character, the only other character of this class being [[Koopa Paratroopa|Paratroopa]].

The [[Mario Tennis (Game Boy Color)|Game Boy Color version]] instead features a Boo in in the [[Boo Blast (minigame)|Boo Blast]] minigame, where the tennis players have to hit Boos. They also appear in the audience at [[Peach's Castle]].

===''Mario Power Tennis''===
Boo is also playable in ''[[Mario Power Tennis]]'', which also provides it a different voice. When he wins a championship, Mario and Luigi would come out with the trophy and Boo would be missing. They look around and the trophy would start to float. Boo then appears under it to Luigi's relief as Mario laughs in amusement. The Mario Bros. themselves are then surrounded and levitated by multiple other Boos as the main Boo flies up to the screen and holds the trophy. Boo's taunt is to wave his racket while laughing. Boo's offensive power shot is the [[Boo Blast (move)|Boo Blast]] and defensive power shot is the [[Boo Brigade Return]].

===''Mario Tennis Open''===
Boo reappears in ''[[Mario Tennis Open]]'', where he is again a playable and starting participant. He is classified as a Tricky characters alongside [[Bowser Jr.]] and [[White Yoshi]].

===''Mario Tennis: Ultra Smash''===
Boo appears in ''[[Mario Tennis: Ultra Smash]]'' as a default playable character. He is once again a Tricky character.

===''Mario Tennis Aces''===
[[File:MTA Models Boo.png|thumb|Boo from ''Mario Tennis Aces'']]
Boo returns as a playable character in ''[[Mario Tennis Aces]]''. Like in previous entries of the ''Mario Tennis'' series, Boo is classified as a Tricky character. His [[Trick Shot]]s are Roundabout and Through It All, while his [[Special Shot (Mario Tennis Aces)|Special Shot]] is Illusion. Boo also has unlockable alternate costumes, coming in the form of visors, that can be unlocked by playing the "Boo Hunt" co-op challenge. In this challenge, the player must hit Boos at the other side of the court to get coins. The visors came in Blue, Green, and Purple and require 2,500 coins, 10,000 coins and 20,000 coins respectively.
{{br}}

==''Paper Mario'' series==
Boos have appeared in every game in the ''[[Paper Mario (series)|Paper Mario]]'' series, where they are usually found in ghost houses, like in the other ''Super Mario'' games. In the first three ''Paper Mario'' games, the Boos appear with a design similar to [[Bigger Boo]] from ''[[Super Mario World 2: Yoshi's Island]]''. In the latter three games, they use their modern appearance from ''Mario Party 4'' and onward.
===''Paper Mario''===
{{quote|I want to hear people shriek and watch them run away yelling! That's what makes Boos happy.|Boo|Paper Mario}}
[[File:PM Boos Throwing the Record.png|thumb|Boos in [[Boo's Mansion]] from ''Paper Mario'']]
{{multiple image
|align=right
|direction=horizontal
|image1=PM Boo Sprite.png
|image2=Herbert.png
|width1=38
|width2=39
|footer=Two kinds of Boos from ''[[Paper Mario]]''
}}
Boos appear in ''[[Paper Mario]]'' as friendly but tricky characters. White Boos live in [[Boo's Mansion]], and tan Boos live at [[Gusty Gulch]]. Their leader is [[Lady Bow]], who lives in Boo's Mansion along with [[Bootler]].

At first, Boos were being eaten by [[Tubba Blubba]]. Some Boos tried attacking the monster to save their friends, but they failed because of Tubba Blubba's "Invincibility". Seeking help from [[Mario]], they captured [[Skolar]], the Star Spirit Mario was trying to save in order to have Mario help them.

In the game, when [[Mario]] arrives at [[Boo's Mansion]], [[Bootler]] tells him to get to the third floor. The Boos have prepared some puzzles for him under the order of [[Lady Bow]] to test him. One puzzle is for Boos to form a rotary circle, throw an item several times and ask Mario to guess who is holding the item. The first time he opens a door a big Boo appears on the screen. In the eastern room of the second floor Boos holding a [[Record (Paper Mario)|Record]] play this trick. In the western room of the second floor, a Boo is guarding a chest box with a [[Weight]] in it. Mario plays the Record to lure the Boo away and uses the Weight on the droplight of the mansion to open the western door on the first floor. Boos in the basement hide in a big chest box in the basement. When Mario opens the chest box, they play the puzzle with [[Super Boots]]. After Mario gets them, he is able to get [[Boo's Portrait]] with which he is able to get to the third floor. There, Lady Bow asks Mario to help the Boos to defeat Tubba Blubba as a condition to free Skolar, and joins Mario's party to assist him. 

A Boo by the name of [[Igor]] also has a shop in the basement, but he will not sell until after Lady Bow joins the party.

In addition, a Boo appears after Mario gets the [[Super Boots]], and tells him how to get the [[Star Piece (Paper Mario series)|Star Pieces]] underground. Additionally, some Boos are flying in the sky who can be seen out of the windows. When Mario is about to set off, two white Boos appear to open the gate to Gusty Gulch under the command of Bow.

In [[Gusty Gulch]], upon [[Tubba Blubba]]'s arrival, the Boos hide except for [[Stanley (Paper Mario)|Stanley]], who is too late and gets caught and eaten by Tubba Blubba.

In the basement of [[Tubba Blubba's Castle]], a brown Boo tells [[Mario]] not to fight [[Tubba Blubba]] until he finds his weak point. According to his word, he sneaked into the castle to look for the weak point. After [[Mario]] gets [[Yakkey]], some tan Boos appear in front of [[Tubba Blubba's Castle]] and, seeing Mario and [[Lady Bow|Bow]] get out and [[Tubba Blubba]] chasing, help the team by blocking the door.

After [[Tubba Blubba]] is defeated, the Boos he has eaten are saved, and Bootler releases Skolar as promised. Boos rejoice, and the background music in Boo's Mansion is replaced with a cheerful one. The Boos at [[Gusty Gulch]] write Lady Bow [[List of letters in Paper Mario#Boos in Gusty Gulch|an admiration letter]], which the player can read at the [[Toad Town Post Office]]. They also begin to talk about a female Boo called [[List of implied characters#Victoria|Victoria]].

After Mario defeats [[Bowser]], two Boos come to [[Peach's Castle]] to see the party, one white and one brown. The white one says he comes to see [[Lady Bow]] in her finery. He thinks that Bow is prettier than [[Princess Peach]]. The brown one says that he is going to have a wedding ceremony after the party. In the end-of-game [[parade]], three white Boos along with [[Bootler]] are carrying [[Tubba Blubba]]'s body.

===''Paper Mario: The Thousand-Year Door''===
[[File:PMTTYD Boo Sprite.png|frame|left]]
Boos return in ''[[Paper Mario: The Thousand-Year Door]]'' as friendly characters as well as enemies for the first time in the series. Some Boos such as [[Lahla]] and [[Peeka]] in [[Rogueport]] can be seen running shops and various casino games.
Enemy Boos are found in [[Creepy Steeple]] and levels 21-29 of the [[Pit of 100 Trials (Paper Mario: The Thousand-Year Door)|Pit of 100 Trials]]. When Mario first enters the steeple there is only one Boo in the room who says that he misses his friends. He will let Mario through only one door (blocking him from using any other doors), where he finds a chest. When he opens it, 200 Boos fly out. The last Boo asks Mario "How many Boos came out of that chest?" If Mario answers correctly the Boo will give him an [[Ultra Mushroom|Ultra Shroom]]. If Mario is wrong the Boo will give him one [[coin]]. Upon returning to the main room, the first Boo is still there. He asks if Mario is going to be mean to him. If Mario answers "No", a bunch of Boos (the same ones from the treasure chest) will start flying around the main room, attempting to swarm Mario. If successful, they will throw Mario out of the Steeple, exactly like the [[Sentinel]]s in [[Tubba Blubba's Castle]]. If Mario Spin Attacks them several times, they merge into an [[Big Boo|Atomic Boo]]. Once the Atomic Boo is defeated (releasing a [[Lucky Start]] [[List of badges in Paper Mario: The Thousand-Year Door|badge]]), Mario can fight Boos in other parts of the Steeple. Even before defeating the Atomic Boo, Boos can still be found, but only when accompanying [[Swoop]]ers.

The original Creepy Steeple Boo sends an [[Mailbox SP#Boo: Mail?|e-mail]] to Mario that thanks him for freeing his friends, despite the fact that they attacked him. He signs the letter "[[The Creepy Steeple Boo]]". More Boos can be found in the Pit of 100 Trials. In this game, Boos attack by becoming invisible and getting close to Mario or the partner, then becoming visible and making a glare at them, causing 3 damage. However, if Mario or his allies gets lucky in battle, the Boo who tried to attack Mario and his partner will be tired out. The game also introduces a more powerful sub-species, the [[Dark Boo]], which can be found in [[Poshley Sanctum]].

Boos can also appear as members of the [[audience]], where they can throw items onto the stage and randomly turn a character in the battle invisible for one turn.

In the [[Paper Mario: The Thousand-Year Door (Nintendo Switch)|remake]], the Boos use their modern voice clips. Additionally, the Creepy Steeple Boo can be later found in the hidden room containing the [[Cookbook]]. When spoken to, he will quiz Mario again with three questions about various parts of the game, and will reward Mario with an item if the latter answers all three questions correctly. This can be done multiple times, each with its own trio of questions.
====Field Tattle====
Outside of battle, [[Goombella]] can use [[Tattle]] only on a Boo found in the foyer of [[Creepy Steeple]] after Mario releases the 200 Boos.
*"''That's a Boo. You think it's one of the Boos from that box?''"

===''Super Paper Mario''===
[[File:Mansion patrol.png|thumb|Boos in the minigame [[Mansion Patrol]] in the Flipside Arcade from ''Super Paper Mario'']]
Boos return as enemies in ''[[Super Paper Mario]]''. In this game, they turn invisible if Mario looks at them, but they turn visible and chase him if he is not looking at them, similar to their behavior in ''Super Mario 64''. To defeat them, the player must approach them from the back and then attack them. Additionally, the [[Flipside Arcade]] houses a Boo themed shooting game, Mansion Patrol. This game has the player shooting Boos, including Dark Boos and occasionally Atomic Boos, to score points. A [[Toad]] frequently appears to give power-ups, as long as the player saves him from his Boo captor. Lady Bow also makes three cameos in this game.

===''Paper Mario: Sticker Star''===
[[File:Boo PMSS.png|frame|left]]
Boos reappear in ''[[Paper Mario: Sticker Star]]''. They only appear in World 4-3: [[The Enigmansion]]. Mario must use the [[Book of Sealing]], given by a [[Toad (species)|Toad]], to seal away every Boo that has escaped. In battle, Boos can make themselves disappear and can slap Mario or they can go up to Mario and scare him by making a scary face. They are able to make Mario [[dizzy]] in this game with their scare attack preventing him from using any of his defensive/dodging stickers. The attack is determined by the sound the Boo makes when it disappears.

Among the normal Boos, there is one golden Boo that drops several Coins after Mario defeats it, which can be found in the safe. This Boo attacks exactly like the normal ones. Another notable Boo is one that is crumpled, which is found in a trash can. In battle, it only has 1 HP and cannot attack. Additionally, a group of eighty-two Boos called a [[Boo Stack]] also appears. Once all the Boos get returned to the book and it is placed in its rightful spot, [[Kamek]] appears and turns all the captured Boos into the mini boss, [[Big Boo#Paper Mario series|Big Boo]]. After defeating the mini-boss, the Boos are put to rest once again and the mansion is restored to its former state. Boos can no longer be fought at this point.

===''Paper Mario: Color Splash''===
[[File:PMCS Boo 10-Stack Idle Animated.gif|thumb|left|A [[Boo 10-Stack]] from ''Paper Mario: Color Splash'']]
Boos return in ''[[Paper Mario: Color Splash]]'' as enemies who can be fought within the [[parallel world]] at [[Vortex Island]], [[Lighthouse Island]] and [[Fortune Island]]. By the time they are first encountered, Mario can instantly defeat them with a hammer [[First Strike]] without entering a battle. In battle, they attack by either hitting Mario or scaring him. They can disappear while in battle, causing all attacks to miss until they reappear. Outside of battle, if one is stared at too long, it will disappear, and then reappear behind Mario. A Boo appears as an NPC in [[Redpepper Crater]], where it is in a hot spring. A [[Boo 10-Stack]] variant also appears.
{{br}}

===''Paper Mario: The Origami King''===
[[File:OrigamiBoo.jpg|thumb|An origami Boo as seen in ''Paper Mario: The Origami King'']]
[[File:Paper Macho Boo.jpg|thumb|left|A Paper Macho Boo]]
[[Folded Soldiers|Origami]] Boos appear as enemies in ''[[Paper Mario: The Origami King]]'', first encountered in the [[Scorching Sandpaper Desert]], but only at night; after Mario has explored the [[Temple of Shrooms]] and put the sun back in the sky, they are replaced by [[Koopa Paratroopa]]s. In battle, Boos will turn invisible right before Mario manipulates the arena, forcing him to memorize their positions. However, they will reveal themselves if they are hit by a Toad's thrown object or shortly before time runs out. In addition, much larger [[Paper Macho Boo]]s appear in the desert at night, replaced by [[Paper Macho Koopa Paratroopa]]s by day. A Paper Macho Boo is also featured as one of the seven opponents on [[Scuffle Island]].
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==''Luigi's Mansion'' series==
===''Luigi's Mansion''===
{{main|List of Boos in Luigi's Mansion}}
[[File:LMBoo.jpg|thumb|left|A Boo in ''Luigi's Mansion'']]
In ''[[Luigi's Mansion]]'' and [[Luigi's Mansion (Nintendo 3DS)|the Nintendo 3DS remake]], Boos serve under [[King Boo]], who is the main antagonist. There are [[List of Boos in Luigi's Mansion|50 Boos]] (51 including King Boo) which Luigi must suck up in the Poltergust 3000. Of these, 15 of them are [[Mini Boo|smaller one]]s that make up the portrait ghost [[Boolossus]], with King Boo as the final Boo. Unlike the other ghosts in the game, Boos will appear in a room, even when the lights are on. When Luigi attacks them, they usually run away, but occasionally twirl into him to cause damage. All of the 36 Boos, excluding King Boo and counting Boolossus as one Boo, have puns in their names. Contrary to the ''Super Mario'' series, Boos hide when Luigi's not looking at them, and they face Luigi when he finds them.

===''Luigi's Mansion: Dark Moon''===
{{main|List of Boos in Luigi's Mansion: Dark Moon}}
Boos appear in ''[[Luigi's Mansion: Dark Moon]]''. They have names that play on "Boo" as in the first game. [[King Boo]] appears, having a similar appearance to that of his debut. They have the ability to create [[Spirit Ball]]s which can make objects invisible until exposed with the [[Dark-Light Device]]. All of the regular missions in the game have a Boo in an object that is invisible, and Luigi must find it by revealing the invisible object with the Dark-Light function of the [[Poltergust 5000]]; the Boo appears after the revealed Spirit Balls have been vacuumed up. However, not all Boos are hidden in invisible objects.

To capture a Boo, Luigi must expose it with the Dark-Light, vacuum and pull on the Boo's tongue, and release it with the {{button|3ds|A}} Button, damaging the Boo as it bounces around the room. When it reaches 0 [[Heart Point|HP]], the Boo can be sucked up; it sticks onto the nozzle, and Luigi presses the Poltergust 5000 against the ground to shove it inside. When Luigi returns to the [[Bunker]] after completing a mission, any captured Boos are sent to the Boo Canister in the [[E. Gadd's Vault#Boo Canister|Vault]]. After all Boos in a mansion have been captured, a bonus mission is unlocked for the corresponding mansion. There are a total of [[List of Boos in Luigi's Mansion: Dark Moon|32 Boos]], 33 if counting King Boo, 10 of which merge into the [[Big Boo]] fought in the [[Treacherous Mansion]].

===''Luigi's Mansion 3''===
{{main|List of Boos in Luigi's Mansion 3}}
[[File:LM3BooArt.jpg|thumb|175px|A Boo in ''Luigi's Mansion 3'']]
Boos return in ''[[Luigi's Mansion 3]]''. Like in previous entries, they have "Boo"-inspired names, and [[King Boo]] returns as the main antagonist. Every floor except the [[Master Suite]] has a Boo to capture, which appears after Luigi has obtained that floor's elevator button. The exact location of each Boo is randomized. To help find a Boo, [[Gooigi]] will begin to vibrate, corresponding with the player's controller, when next to the room with the Boo in it. There is also an item in the game known as a [[Boo Finder]], which reveals the location of a single Boo. Once Luigi enters the room with the Boo, the music will change and he must uncover the object with the strongest vibrations, which causes the Boo to appear and seal all exits until caught. If a wrong object is uncovered, the Boo will launch a swarm of bats at Luigi and flee to a different room. Once revealed, Boos attack by either spinning towards Luigi to deduct 20 HP or by throwing a [[Bomb (object)|bomb]] at him. To capture the Boo, Luigi must expose it with the Dark-Light device, then pull on its tongue and slam it repeatedly. All Boos have 20 HP.

==''Super Smash Bros.'' series==
{{main-wiki|SmashWiki|Boo}}
In the [[Super Smash Bros. (series)|''Super Smash Bros.'' series]], Boos mostly appear in the form of collectible items. In ''[[Super Smash Bros. Melee]]'', a Boo appears as a collectible [[Trophy (Super Smash Bros.)|trophy]]. In ''[[Super Smash Bros. Brawl]]'', there is another trophy of Boo, as well as a [[Sticker (Super Smash Bros. Brawl)#Boo|sticker]] depicting its artwork from ''Mario Tennis''. In both ''[[Super Smash Bros. for Nintendo 3DS]]'' and ''[[Super Smash Bros. for Wii U]]'', Boos once again received their own collectible trophy; furthermore, ''Super Smash Bros. for Wii U'' gave one an item in [[smashwiki:Smash Tour|Smash Tour]], where using it allows the player to begin a battle while invincible. In ''[[Super Smash Bros. Ultimate]]'', there is a Novice-class Neutral-type primary [[Spirit (Super Smash Bros. Ultimate)|spirit]] of a Boo, using its artwork from ''[[New Super Mario Bros. U]]'', and it can be enhanced to [[King Boo]] at level 99. In [[smashwiki:Adventure Mode: World of Light|World of Light]], the Boo spirit appears in the [[smashwiki:Dracula's Castle (World of Light)|Dracula's Castle]] sub-world of the [[smashwiki:Dark Realm|Dark Realm]]. The spirit battle takes place on the [[Mushroom Kingdom U]] stage, with an invisible grayscale [[Kirby]] as the puppet fighter.

Boos appear in the background of the [[Luigi's Mansion (stage)|Luigi's Mansion stage]] in ''Super Smash Bros. Brawl'', ''Super Smash Bros. for Wii U'', and ''Super Smash Bros. Ultimate''. Here, they are very briefly seen flying out the [[Luigi's Mansion (location)|mansion]] when a part of it is knocked down.

==''Mario & Luigi'' series==
===''Mario & Luigi: Superstar Saga'' / ''Mario & Luigi: Superstar Saga + Bowser's Minions''===
[[File:Castleinterior.png|thumb|A Boo chases the Mario Bros. in ''Mario & Luigi: Superstar Saga''.]]
In ''[[Mario & Luigi: Superstar Saga]]'', Boos are enemies that only appear in [[Bowser's Castle]]; they aid [[Bowletta]] along with the rest of the minions who believe her to be Bowser. Outside of battle, they hover around, attacking Mario and Luigi when they are not looking. However, they look away if Mario or Luigi make eye contact. The Boos also show the ability to teleport. In battle, a Boo has two attacks. For the first attack, the Boo will teleport in front of one of the brothers and attempt to bite him. For the second attack, it will fly up into the air and swoop into one of the Mario Bros., which can even [[Prohibited Command|prohibit the use of certain moves or items]]. The former attack can be countered with Mario or Luigi's hammer, whereas the latter can be dodged or countered by jumping. In either of these attacks, if the Boo makes a face, it will target Luigi, if it does not, it will target Mario. Boos are weak to [[Firebrand]] and [[Fire Bros. (move)|Fire Bros.]] They also have low HP, but very high defense.

[[File:MLSS Miner Boo.gif|frame|left]]
Boos wearing mining helmets and brandishing pickaxes also appear in levels 4 and 5 of [[Mysterious Mine Carts]]. If these Boos touch Mario, they will cause the loss of a diamond. They will slowly shrink until they disappear if the flashlight is pointed at them.

Boos appear in the main game and in ''Minion Quest: The Search for Bowser'' from ''[[Mario & Luigi: Superstar Saga + Bowser's Minions]]''. Boos are flying troopers, and attack by ramming into enemies. Their [[Special Skill (Mario & Luigi series)|Special Skill]], Evasion Cloak, allows them to increase their evasion, depending on how filled the meter that is shown becomes. [[Captain Boo]] appears as a playable captain in the game. When a Boo appears as a captain, they are able to attack the other captain from behind, using [[Sneak Attack]].

[[File:Boo Statue M&LSS sprite.png|frame|right]]
There are also [[Boo Statue]]s which become invisible and cannot be interacted with when looked directly at. Mario and Luigi must use the [[Tickle]] move to push them while facing backward.

===''Mario & Luigi: Partners in Time''===
[[File:PiT Boo.gif|frame]]
During the events of ''[[Mario & Luigi: Partners in Time]]'', Boos appear in [[Bowser's Castle]] of the past. In the field, Boos attack the same way as they did in ''Mario & Luigi: Superstar Saga''. In battle, a Boo attacks by peeking through one of its eyes; peeking with the right eye is Mario, and with the left eye, Luigi. The Boo reappears behind the corresponding bro and charges from behind; this can be avoided or countered with a jump. Boos also appear during the battle with [[Sunnycide]]. While flipped on its back, Sunnycide can summon a Boo to attack Mario or Luigi, which can be countered with a hammer. Also, when a [[Handfake]] has a [[Bowser]] sign, a Boo or a [[Fly Guy]] carries a flame from Bowser's mouth. Dark Boos are found in the [[Gritzy Caves]].

===''Mario & Luigi: Bowser's Inside Story'' / ''Mario & Luigi: Bowser's Inside Story + Bowser Jr.'s Journey''===
[[File:Bis Boo plate sprite.PNG|frame|left|A Boo holding a plate]]
{{multiframe
|[[File:BowserMemoryBoo.png]] [[File:MLBISBJJBowserMemoryBoo.png]]
|A digital Boo.
|align=right
|size=75
}}
Boos make a reappearance in ''[[Mario & Luigi: Bowser's Inside Story]]''. They appear in [[Bowser's Castle#Mario & Luigi: Bowser's Inside Story / Mario & Luigi: Bowser's Inside Story + Bowser Jr.'s Journey|Bowser's Castle]], where they have been brainwashed by [[Fawful]] along with the rest of Bowser's minions once he took over the castle. When Bowser gets to have a feast as a reward for beating [[Midbus]] at the [[Fawful Theater]] show, three Boos serve him food cooked by Fawful himself. However, Bowser is tricked into eating too much food and ends up getting fat, which results in him getting stuck in the floor due to his weight. Boos reappear later in the game to help many of the brainwashed minions of Bowser push the Fawful statue against him. In addition, a Boo appears whenever Bowser gets a [[level up]]. The Boo (just like the [[Fishin' Lakitu]] in Mario's or Luigi's level up screen) holds the circle for getting a bonus upgrade for the stat of the player's choice.

An odd thing shown in the game is a Boo and [[Koopa Troopa]] in love with each other in Bowser's Castle. They not only love each other, but also love Fawful due to the brainwashing that was put on the minions.

[[Yikk]], a ghost who appears in the same game at the [[Tower of Yikk]], explains that he researches Boos. He even builds a [[Boo-ray Machine|machine]] to visualize Boo transparency waves before he passed away.

During the fight with [[Bowser Memory ML]], Bowser Memory L has an attack that involves a digital Boo chasing him around. The Boo can be jumped on by either Mario or Luigi to stop the attack prematurely.

[[File:MLBISBJJBoo.png|frame]]
Boos return in ''[[Mario & Luigi: Bowser's Inside Story + Bowser Jr.'s Journey]]'', where they additionally are found as enemies and recruitable allies in the ''Bowser Jr.'s Journey'' mode. Their special attack is Discord, which [[SPD-Down|lowers the speed]] of enemies.

===''Mario & Luigi: Dream Team''===
[[File:M&LDT Boo Biscuit.png|frame|left]]
While Boos themselves do not appear in ''[[Mario & Luigi: Dream Team]]'', an item named [[Boo Biscuit]] does.

===''Mario & Luigi: Paper Jam''===
[[File:MLPJShinyPaperBoo.png|frame|left]]
Boos appear in ''[[Mario & Luigi: Paper Jam]]'' in a minigame where the player has to save a Toad by running away from a Boo and avoiding firebars and bombs. Like in many other games, this Boo will stop if the Mario Bros. look at it, and will follow them if they look away. Boos can also be seen carrying Papercraft Boos, along with Papercraft King Boo. Their [[Paper Boo|paper versions]] also appear as regular enemies in the haunted side of [[Gloomy Woods]]. [[King Boo]] also appears as a boss in [[Gloomy Woods]]. [[Boo Biscuit]]s also return from ''[[Mario & Luigi: Dream Team]]''.
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==''Mario vs. Donkey Kong'' series==
===''Mario vs. Donkey Kong''===
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Boos appear in ''[[Mario vs. Donkey Kong]]'', acting similarly to their other appearances in platforming games. They only appear in both segments of [[Level 4-4 (Mario vs. Donkey Kong)|Level 4-4]] and in [[Level 4-4+]]. They cannot be defeated, and if they manage to defeat [[Mario]] or the [[Mini Mario (toy)|Mini-Mario]], the Boo will grow and stick its tongue out.

In the game's [[Mario vs. Donkey Kong (Nintendo Switch)|Nintendo Switch remake]], Boos are more clearly depicted with a toylike appearance. Also, in co-op play, they float towards [[Toad]] if his back is turned away, but stop moving if he looks at them.<ref>{{cite|author=NintendoEurope|date=January 26, 2024|title=Find out if two heads really are better than one in #MarioDonkeyKong's new co-op mode! Pass a controller to a friend and tackle the puzzle-platforming challenges together (and let Toad get a bit of glory too!).|url=x.com/NintendoEurope/status/1750866179407655354|publisher=X|accessdate=February 1, 2024}}</ref>

===''Mini Mario & Friends: amiibo Challenge''===
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In ''[[Mini Mario & Friends: amiibo Challenge]]'', Boos have a toylike appearance and float in mid-air, with some moving on a straight path (vertically or horizontally) from side to side, while others staying in one place. They are invincible and, when in their active state, harmful to touch. However, they become harmless when they enter the light coming from a [[Candle]]. In this state, they are also forced to stop in place and cover their eyes, much like an actual Boo does when a character faces it in platform games, and the [[Mini]]s are able to pass through them.

Boos are present in all levels of [[Moonlight Mansion]], as well as levels [[Star 3]] and [[Star 5]] in the [[Star World (Mini Mario & Friends: amiibo Challenge)|Star World]].
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==''Mario Pinball Land''==
[[File:Bigboopinball.png|thumb|left|A group of Boos with [[Big Boo]] in ''Mario Pinball Land'']]
In ''[[Mario Pinball Land]]'', Boos appear in certain areas in the game. [[Mario]] cannot hit them at the front because they will become transparent as Mario passes through them. If Mario hits one of the Boos on its back, the Boo disappears and it is worth 2,000 points. They occasionally will disappear and reappear to another spot in the area.

A Big Boo also appears as one of the game's bosses. He is the boss of the haunted house and can only be damaged by hitting it from behind.
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==''Dance Dance Revolution: Mario Mix''==
[[File:DDRMMboos.jpg|thumb|left|A Boo with [[Mario]] from ''Dance Dance Revolution: Mario Mix'']]
Some Boos make appearances in ''[[Dance Dance Revolution: Mario Mix]]'' in both regular and giant varieties. Their objective is to try to make [[Mario]] miss a step. If successful, they block Mario's next move. Mario is able to step on regular Boos to hold them back, but he cannot do the same to their gigantic counterparts.
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==''Mario Baseball'' series==
[[File:Boo-Batting-MSS.png|thumb|left|Boo prepares to bat in ''Mario Super Sluggers'']]
Boo makes its first baseball appearance in ''[[Mario Superstar Baseball]]''. It is on Wario's team as a starter. Boo is tied with Peach with its pitching, losing only to [[Bowser]] and [[Waluigi]]. Its special running and fielding move is a [[Super Jump (Mario Baseball series)|Super Jump]]. Its running and batting are weak, but its fielding is very poor. The only worse fielder in the game is [[Bowser]].

Boo makes another appearance in ''[[Mario Super Sluggers]]''. It is on Wario's team once again, and it can be unlocked in [[Wario City]] by finding it in between boxes and completing its challenge. Like its predecessor, Boo has the highest ranked pitch in the game, along with Peach (9/10). Despite its pitching being very high, its stamina is very poor, but its other stats range from average to low. Boo displays good chemistry with [[King Boo]], [[Shy Guy]], [[Magikoopa]], and [[Blooper]]. It has bad chemistry with [[Mario]], [[Luigi]], [[Yoshi]], [[Baby Mario]], [[Baby Luigi]], [[Baby Peach]], and [[Baby Daisy]].

There is a new item named [[Mini Boo]]s that, when activated, turn the ball invisible for a short period of time. If used against a computer, the player stops moving until the Boos go away. If used when a special hit is in effect, the Boos do nothing.
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==''Super Princess Peach''==
[[File:SPPBoo.png|frame]]
Boos in ''[[Super Princess Peach]]'' act like in the ''Super Mario'' series: they hide their face when Peach looks at them but attack when Peach has her back turned. However, there is an angry variety called the [[Mad Boo]], which attacks the opposite way. They attack when Peach looks at them, and gander around for her when she looks away. Aside from Boos, Big Boos, [[Mad Big Boo]]s, and [[Blindfold Boo]]s are introduced as enemies, and King Boo appears as a boss.

==''Mario and the Incredible Rescue''==
[[File:MarioAndIncredibleRescue.jpg|thumb|120px|Two Boos appear on the front cover of ''Mario and the Incredible Rescue'']]
Boos make an appearance in the chapter book ''[[Mario and the Incredible Rescue]]''. The cover features two Boos. One of the Boos is from ''[[Mario Kart: Super Circuit]]'' and the other is a mirrored Boo from ''[[Luigi's Mansion]]''. The book never uses their proper name, only referring to them generically as '''ghosts'''. Boos capture [[Princess Peach]] and take her to [[Bowser's Castle]]. Mario also sees a vision of Princess Peach being caged and surrounded by six Boos. Boos are eventually defeated by Mario at the end of the book. To defeat them, Mario casts a spell on them and sends them flying out of the castle.
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==''Mario Hoops 3-on-3''==
Boo appears in ''[[Mario Hoops 3-on-3]]'' as an unlockable character of the Tricky type. Its special ability is the [[Thriller Dunk]]. Boo can be unlocked by completing the [[Flower Tourney]] on hard difficulty.

==''Mario Strikers Charged''==
[[File:Boo Orange Yoshi MSC.jpg|thumb|left|Boo from ''Mario Strikers Charged'']]
In ''[[Mario Strikers Charged]]'', Boos are one of the sidekick options to the many captains. They appear with a helmet with the logo of their team captain. Boos are classified as a playmaker. The only other playmaker sidekicks are Toads. Their skillshot is [[Possess]]. The given description of the Boos is: "''This ghost can fly up and down the sidelines with great speed, using precise and accurate passing to lead his team to victory. His long-distance shots are quite weak though and his hits are not very powerful. If Boo gets a chance, he can Possess the ball and score at will.''"
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==''Mario & Sonic'' series==
{{multiframe|align=left|[[File:BooMASATOG.png]]|size=130|A sprite of a Boo from the Nintendo DS version of ''Mario & Sonic at the Olympic Games''}}
In the [[Mario & Sonic (series)|''Mario & Sonic'' series]], Boos mainly appear in a few events, sometimes also as audience members. In the [[Wii]] version of ''[[Mario & Sonic at the Olympic Games (Wii)|Mario & Sonic at the Olympic Games]]'', Boos appear as an item in [[Dream Race (Mario & Sonic at the Olympic Games for Wii)|Dream Race]], where they temporarily follow whoever is in first place, or second if the player in the lead uses it, causing them to lose speed. It is possible for multiple Boos to follow a character at once, causing them to remain at a lower speed, but a [[Power Sneakers|High Speed]] item can remove them. In the [[Mario & Sonic at the Olympic Games (Nintendo DS)|Nintendo DS version]], Boos penalize the player if they perform two consecutive fouls in the [[100m (Mario & Sonic at the Olympic Games for Nintendo DS)|100m]], [[400m (Mario & Sonic at the Olympic Games for Nintendo DS)|400m]] or [[400m Hurdles (Mario & Sonic at the Olympic Games for Nintendo DS)|400m Hurdles]] events, and in [[Dream Basketball]], a Boo blocks one of the baskets if a [[Chaos Emerald]] is used. Both versions of ''Mario & Sonic at the Olympic Games'' include Boos as part of the audience in various events. In the Nintendo DS version of ''[[Mario & Sonic at the Olympic Winter Games (Nintendo DS)|Mario & Sonic at the Olympic Winter Games]]'', Boos are items in three events: [[Ski Cross Racing]], where they can steal [[Ring (Sonic the Hedgehog)|Rings]] and items from players ahead of the user; [[Extreme Snowboarding]], where Boos steal items from opponents in front and deplete the energy in their trick gauge; and [[Ski Shooting]], where Boos will simply steal an item from an opponent if they have any. In the Nintendo 3DS version of ''[[Mario & Sonic at the Rio 2016 Olympic Games (Nintendo 3DS)|Mario & Sonic at the Rio 2016 Olympic Games]]'', Boos appear in [[Archery Plus]], where they carry around the targets and disappear upon being shot.

Boos appear in some of the minigames. In the Nintendo DS version of ''Mario & Sonic at the Olympic Games'', Boos appear in two minigames: [[Conveyor Belt (minigame)|Conveyor Belt]], as one of the characters needing to be sorted, and [[Shoot!]], as one of the enemies to be hit. In ''[[Mario & Sonic at the London 2012 Olympic Games (Wii)|Mario & Sonic at the London 2012 Olympic Games]]'', Boos also appear in some minigames in the London Party mode, which itself has some Boos that can be spoken to play minigames and earn stickers.
[[File:M&S 2012 The Ghostly Tower.png|thumb|King Boo talking to a Boo in [[The Ghostly Tower]]]]
Boos have also had some of their own collectible items. In the Wii version of ''Mario & Sonic at the London 2012 Olympic Games'', one of the unlockable [[Mii]] outfits is a jersey featuring a Boo design. In the [[Nintendo 3DS]] version of ''[[Mario & Sonic at the London 2012 Olympic Games (Nintendo 3DS)|Mario & Sonic at the London 2012 Olympic Games]]'', a [[List of badges in Mario & Sonic at the London 2012 Olympic Games (Nintendo 3DS)|badge]] of a Boo can be obtained from the badge machine.

In [[Nintendo 3DS]] version of ''[[Mario & Sonic at the London 2012 Olympic Games (Nintendo 3DS)|Mario & Sonic at the London 2012 Olympic Games]]'', a Boo first appears in the Story Mode trying to scare people away from the [[Tower of London]] with the [[Phantasmal Fog]], and is then followed by [[Sonic]] and [[Tails]] who challenge the Boo and King Boo to an Olympic [[Event]], with the Boos fleeing when they lose. A single Boo also appears at the opening ceremony. A Boo also appears in [[Mario's Defeat?!]], in which it fails to bring Mario to the [[London Tennis Club]] but helps set up the match with a Goomba transformed to look like Mario, and later celebrates with the other minions when they notice that Bowser seems to be back to his usual self.
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==''Mario Sports Mix''==
[[File:LMSportsMix.png|thumb|left|Boos seen in the background in ''Mario Sports Mix'']]
Boos appear in ''[[Mario Sports Mix]]''. They appear as the only members of the crowd in [[Luigi's Mansion (location)#Mario Sports Mix|Luigi's Mansion]] circling around the court. Their appearances are in [[Mario Sports Mix#Basketball|Basketball]] and [[Mario Sports Mix#Volleyball|Volleyball]] matches and their laughs can also be heard during the game. Mainly, they can be heard when the player gets a point.
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==''Captain Toad: Treasure Tracker''==
[[File:TreasureTracker-E32014-Screenshot11.png|thumb|A shy Boo in ''Captain Toad: Treasure Tracker'']]
[[File:Boo CTTT.png|150px|thumb|left|A Boo in ''[[Captain Toad: Treasure Tracker]]'']]
Boos return in ''[[Captain Toad: Treasure Tracker]]'' and its Nintendo Switch and Nintendo 3DS [[Captain Toad: Treasure Tracker (Nintendo Switch / Nintendo 3DS)|ports]], functioning the same as they did in ''Super Mario 3D World'' with a few minor tweaks. Despite still chasing the player when not watched, Boos and [[Big Boo]]s can easily be destroyed with Toad's or Toadette's headlamp. Additionally, using a [[Double Cherry]] to shine two headlamps on a Boo will defeat it much faster, within a quarter of a second.

Interacting with Boos on the touch screen or with the pointer functionality will cause them to disappear until the player points away. Unlike most enemies in the game, holding the pointer on Boos for however long will not reward a coin.
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==''Mario Sports Superstars''==
[[File:Card SuperRare Boo.png|thumb|A Super Rare Boo card from ''Mario Sports Superstars'']]
Boo appears as one of the starter captain-type characters in ''[[Mario Sports Superstars]]''. In most sports, he is classified as a Technique type character, sharing this attribute with [[Princess Peach|Peach]], [[Princess Daisy|Daisy]], and [[Waluigi]]. As such, he excels in aspects such as shot accuracy or horse control. In tennis, Boo is instead a Tricky type character, as per his appearances in the ''Mario Tennis'' series, alongside [[Bowser Jr.]] and [[Rosalina]]. His rallies have a tendency to curve, making it tricky for the opponent to predict the trajectory of his shots. In golf, Boo's default drive is 213 yards, and his shots travel medium-low in a draw trajectory.
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==''Mario + Rabbids'' series==
===''Mario + Rabbids Kingdom Battle''===
[[File:MoonlightSonata MarioRabbids.png|thumb|left|A Boo in [[Moonlight Sonata]] from ''Mario + Rabbids Kingdom Battle'']]
Boos appear as obstacles in certain areas in ''[[Mario + Rabbids Kingdom Battle]]''. They warp to certain areas during the turn transition between the heroes and enemies. If a Boo converges on a character, it will follow said character and force them to warp to a random spot on the battlefield along with the Boo. Additionally, one of [[Rabbid Mario]]'s Melee weapons has a design based on a Boo, and in [[Spooky Trails]], several Boos can be found ensnared by ghostly chains, as well as a [[Boo Balloon]] that was merged with a [[Rabbid]] and a phonograph, becoming the [[Phantom (boss)|Phantom]].

===''Mario + Rabbids Sparks of Hope''===
While no Boos appear in ''[[Mario + Rabbids Sparks of Hope]]'', the laugh of one can be heard if the [[Spark (Mario + Rabbids Sparks of Hope)|Spark]] [[Vampastra]] applies its Vamp Attack ability to Mario, and he uses his Dual Slingers to attack. In the [[Rayman in the Phantom Show]] DLC, Boos make cameos as the Spooky Trails banners from the first game.
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==''Dr. Mario World''==
[[File:DMW Dr Boo Artwork.png|thumb|Artwork of Dr. Boo in ''Dr. Mario World'']]
The Boo assistant was added on October 31, 2019. Its effect in stage mode is to fill the skill meter faster when yellow [[virus]]es are eliminated, where it fills more at higher levels. The percentage determines the number of points the skill meter fills, so for example at level 3, it fills 30% faster, meaning that for each yellow virus eliminated, an extra 0.3 points is added to the skill meter. In versus mode, its effect is to increase the speed the skill meter fills for both the user and their opponent, in which the amount of points required to fill the skill meter is reduced by the listed percentage. If both players use this assistant, the effect stacks. The resulting amount of points required to fill the skill meter is rounded down to the nearest round number.

A Boo was added as a doctor under the name '''Dr. Boo''' in ''[[Dr. Mario World]]'' on September 24, 2020. His skill is represented by the Boo shielding his face, after which he shows his face and tongue. In stage mode, he immediately eliminates objects in a random 2 x 2 area, similar to [[Fire Mario|Dr. Fire Rosalina]]'s skill but it affects a smaller area. In versus mode, he eliminates objects in a 1 x 1 area at level 1, a 2 x 2 area at level 2 and a 3 x 3 area at level 3 to 5 (the skill meter fills faster at higher levels). This skill prioritizes areas that contain [[virus]]es, but if there are no more viruses, the area in which is targeted will be random as long as it contains at least one object.

==Other appearances==
===''The Legend of Zelda: Link's Awakening''===
{{main-wiki|ZeldaWiki|Boo|Zelda Wiki}}
[[File:TLOZ LA remake Boos.jpg|thumb|Boos as they appear in the remake of ''The Legend of Zelda: Link's Awakening'']]
Boos in ''[[The Legend of Zelda: Link's Awakening]]'' only appearing in a dark room in the games' second dungeon, [[zeldawiki:Bottle Grotto|Bottle Grotto]]. They actively chase [[Link]] regardless of whether he is facing them or not; if Links swings his sword at them, they disappear and reappear at a different location. After Link lights up the room, they become vulnerable and can then be defeated with [[zeldawiki:Magic Powder|Magic Powder]]. In the [[Nintendo Switch]] remake of the game, they now use their voice clips from the ''Super Mario'' franchise, and a Boo figure can be won from the [[zeldawiki:Trendy Game|Trendy Game]] after clearing the [[zeldawiki:Key Cavern|Key Cavern]] and placed in the [[zeldawiki:Quadruple|Quadruples]]' house. The text that appears upon acquiring the figure reads, "''You got a Boo figure! As spooky ghosts go, this one's pretty cute!''"

===''Minecraft''===
[[File:Minecraft Mario Mash-Up Boo.jpg|thumb|left|Boo as it appears in ''Minecraft'']]
Additionally, in the Super Mario Mash-up in ''[[Minecraft]]'', Ghasts are replaced by Boos.

===''Monopoly Gamer''===
In ''[[Monopoly Gamer]]'', Boo is a playable character, though it is sold separately as a "Power Pack" expansion figure.
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==Unused appearances==
===''Super Mario Odyssey''===
Boos [[List of Super Mario Odyssey pre-release and unused content|were going to appear physically]] in ''[[Super Mario Odyssey]]'', as one is seen in concept art for the game, but they were removed from the game,<ref>{{cite|author=Brian|date=October 3, 2018|title=New Super Mario Odyssey concept art shows a ton of scrapped costume ideas|url=nintendoeverything.com/new-super-mario-odyssey-concept-art-shows-a-ton-of-scrapped-costume-ideas/|publisher=Nintendo Everything}}</ref> making this game the first game in the ''Super Mario'' series to not contain Boos since ''[[Super Mario Land]]''. However, [[Princess Peach|Peach]] wears a Boo mask on the side of her head when she visits [[Bowser's Kingdom]], a common way to wear masks of ''{{wp|yōkai}}'' in festivals in Japan.

===''The Super Mario Bros. Movie''===
Boos were planned to appear in the film, as they can be seen in early concept artwork for the [[Dark Land]]s, but they were removed from the final release.<ref>{{cite|author=GameXplain|date=April 23, 2023|title=Toadsworth & Toadette were in the Super Mario Bros. Movie?! Concept Art LEAK Reveals Cuts & Changes|url=www.youtube.com/watch?v=b2KZXJg3ncA|publisher=YouTube|accessdate=April 23, 2023}}</ref> However, their leader, [[King Boo]], makes an appearance during the wedding between [[Bowser]] and [[Princess Peach|Peach]].

==References==
<references/>

{{Histories}}
[[Category:Histories|Boos]]