Boo

"Ghosts... ...don't... ...DIE! Heh, heh, heh! Can you get out of here... ...alive?"

- Boo

The Boo (originally known as Boo Diddley) is a common ghost-enemy in the Mario series that first appear in Super Mario Bros. 3. They are a type of white spherical ghost with menacing and constantly open mouths and also small "arms" of some sort. Goombario's tattle for the Boo Igor in Paper Mario states: "He probably was a merchant before he became a Boo.", implying that current Boos may have once been living beings. It was revealed in Super Mario Galaxy that they speak in Booish.

''Super Mario Bros. 3
Boos first appear in Super Mario Bros. 3. Then, they are referred to as Boo Diddleys, a pun off the late former rock star Bo Diddley. However, future games refer to them only as Boos. The Boo shields its face if Mario or Luigi look at it, but it would start to chase Mario or Luigi if they look away. Boos are unable to defeat, unless the two are equip with a Hammer Bro. Suit, Koopa shell, or Starman. The game also had Stretches, which are Boos with very long bodies that live in the Fortresses throughout the kingdom.

''Super Mario World
In Super Mario World, there are Ghost Houses, which contain many Boos. These Boos retain their usual pattern of attack from Super Mario Bros. 3 and sometimes make faces at Mario or Luigi. This game also introduces many new sub-species of Boo, the Boo Buddy Block, Boo Buddy Snake, Boo Buddy Swarm, Circling Boo Buddies, and Disappearing Boo Buddies. It also introduces a giant version of the Boo, the Big Boo, and a ghost-like Lakitu called a Fishin' Boo.

''Super Mario 64
Boos make a starring appearance in the level, Big Boo's Haunt, in Super Mario 64. A group of Boos can be found in the Castle Gardens (holding Red Coins in the DS version). After collecting twelve Power Stars, Mario is able to enter Big Boo's Haunt by going into the little cage a certain Boo drops. A portal to this course is hidden inside a Big Boo. After Mario attacks it once, a small cage falls out of the Boo, and Mario can jump inside of it. He also battles Big Boo many times here. Additionally, when the Boos look at Mario, they attempt to hide by becoming partially invisible. In the invisible Boo; the player can see a Coin or a Blue Coin as this was an add-on to the Boos' physics. To defeat them, a punch or kick from behind is needed. Unfortunately for them, Mario can also defeat them with a ground pound. They can also be defeated by an explosion.

''Super Mario Bros. Deluxe
While Boos did not appear in the original Super Mario Bros., Boos appeared in Super Mario Bros. Deluxe as the main enemy in the "You VS. Boo" mode. The goal was to reach the flagpole before the Boo. After defeating Boo a certain amount of times, he flies away and a Green Boo replaces him; after that Boo is defeated, a Red Boo takes its place, and finally, a Black Boo with a yellow outline appears. Each new Boo is faster than the one before it, meaning the plain White Boo is the slowest while the so-called "Legendary Black Boo" is the fastest and hardest to defeat.

''Super Mario Sunshine
Boos return in Super Mario Sunshine terrorizing the residents of Hotel Delfino. In this game, they could be stunned by F.L.U.D.D., and defeated by being jumped on. They also disguise themselves as coins. It turns out that Hotel Delfino has mysteries, including flipping floor tiles, a magic painting, and a flipping bookcase. Mario treks through the hotel, and solving its mysteries. Eventually, he finds King Boo in the basement of the Casino, and has to battle him. He can defeat him by throwing a Chili at him, and then throwing another piece of fruit at him. Mario has to do this three times before he finally falls. Boos can also disguise themselves as Shadow Mario, while the real Shadow Mario runs from Mario. Their appearance had just one change, blue circles surrounding their black pupils. Red Boos also appear and can be turned into a platform if sprayed by F.L.U.D.D..

''Super Mario 64 DS
In Super Mario 64 DS, Boos keep the same role they did in Super Mario 64. However, Mario can find a Luigi Painting, which will take him to the Big Boo Battle level on the Balcony. After reaching the end, by following the cackle of King Boo, he makes it to a room with a mirror at the end of it. He then has to battle King Boo. However, King Boo is invisible and the only way for Mario to see him is by looking in the mirror, making it harder to hit him. After hitting him three times, Mario gains the key to the room in which Luigi is trapped in, and proceeds to free Luigi. In the English version of the game, King Boo is erroneously referred to as "Big Boo." Yoshi cannot defeat them in this game. Ground Pounding yields no results, and eating them simply causes Yoshi to spit them back out. Fortunately, the mustached plumbers can hit Boos with ground-pounds.

''New Super Mario Bros.
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. They appear like they usually do, shy. The game also introduces the Balloon Boo, which were normal Boos who could suck up the air, and become much bigger (4-5 times their size). Broozer, the boxing ghost, first appears in this game as well. An icon of a Boo covers the lower screen in Ghost Houses.

''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 only be defeated 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), and they cannot be defeated by Mario's spin or jump attack. However the spin attack can throw a Boo around Mario, knocking it off course temporarily or into a light. Strangely, if a Boo catches sight of Mario while he is Boo Mario, it appears to develop an attraction toward Mario, meaning that it is likely female. If a Boo hits Mario while he is in the Boo Suit, Mario loses the suit, but does not lose any health. Boos can also be found underwater in the Bigmouth Galaxy in this game. While underwater, Boos attack just by swimming back and forth, similar to Cheep-Cheeps, and damage Mario if they touch him. These Boos could be defeated only by pointing at them with the light of the Golden Shell and would rapidly multiply after a while. Also, a Boo called the Spooky Speedster is found in two areas of the game. Mario must race him to win a Power Star. This game also introduces a new kind of Boo, called the Bomb Boo, it is similar to a normal Boo, but is black with yellow eyes and can be grabbed by its tongue if Mario uses his spin attack on it. Spinning again will hammer-toss it into statues and enemies upon which it will blow up on impact destroying the statues and damaging enemies. However, if Mario holds onto the Bomb Boo too long, it will blow up and Mario will take damage.

New Super Mario Bros. Wii
Boos reappear in New Super Mario Bros. Wii in various ghost houses that have appeared in Super Mario World throughout the game. They behave the same way as they did in New Super Mario Bros and, just like before, they are invincible, unless the player has a Star power-up. Big Boos also reappear along with Broozers. Circling Boo Buddies can also be found in a small amount 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 map, a single Boo will be watching Mario, and will taunt him as he enters. If he is 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
Boos reappear in the game Super Mario Galaxy 2. They behave the same way they did in its predecessor however the coins are unviewable when Mario looks at them. They are found in haunted levels such as Haunty Halls Galaxy and Boo Moon Galaxy. The underwater Boos from the prequel also appear in this game, in the Battle Belt Galaxy and Slimy Spring Galaxy.

''The Adventures of Super Mario Bros. 3
Boos made infrequent appearances in The Adventures of Super Mario Bros. 3 television series, which depicted them as having a somewhat more menacing appearance. Like in the game the show was based on, Boos worked for Bowser and often aided 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 were referred to as 'Boodidlies' which was their original name before it became Boo.

Super Mario World television series
In Super Mario World, Boos, who were completely redesigned, appear in the episodes "Ghosts 'R' Us", in which a gang of Boos, as well as a Big Boo, appear to chase Yoshi through Wizardheimer's Haunted House, "The Night Before Cave Christmas", and when Yoshi sees one and he runs off screaming, and "The Yoshi Shuffle" in where several boos appear in the audience during the episode.

''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 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 and that 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 Peach's wedding.

Super Mario-Kun
Boos made an appearance in some of the Super Mario-Kun comics. In issue number 25, Lady Boo appeared on the cover. Many of Mario's other partners appeared on the cover, including Goombario, Kooper, Eldstar, and Twink. This issue was based on Paper Mario. In issue number 26, Lady Boo did not appear on the cover, but in issue number 27, she reappeared on the cover. Both of these issues were based off Paper Mario, too. In a Super Mario Galaxy issue, Boo Mario appeared on the cover along with more of Mario's transformations.

Mario and the Incredible Rescue
Boos made 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. They were known as "ghosts" in the book. Boos captured Princess Peach and took her to Bowser's Castle. Mario saw a vision of Princess Peach in a candlelight being caged and surrounded by six Boos. Boos were eventually defeated by Mario at the end of the book.

Mario Kart series
In the Mario Kart series, the Boo is used as a very tactical item, first appearing in Mario Kart 64. When activated, the Boo selects a racer with the best item in reach, steals the item and gives it to the player. At the same time, the player turns invisible and therefore is completely invulnerable for a short period of time. While invisible, the player can pass the other racers more easily by simply going through them. If no other players have any items, the Boo will return empty handed. Additionally, in Mario Kart: Super Circuit, Boo also slowed down the leading racer and in Mario Kart DS, using the Boo wouldn't make the player lose any speed when driving off-road, so various shortcuts can be exploited. They do not appear as items in Mario Kart: Double Dash!! and Mario Kart Wii. Although King Boo is a playable character for the GameCube and Wii versions.

Mario Baseball series
Boo makes its first baseball appearance in Mario Superstar Baseball. It is on Wario's team as a starter. Boo has the highest ranked pitch in the game, along with Waluigi and Peach. Its special running and fielding move is a Super Jump. The only worse fielder in the game is Bowser. Boo make 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) and averages other moves.

''Super Mario Land 2: 6 Golden Coins
Boos appear in Super Mario Land 2: 6 Golden Coins. These Boos are relatively unchanged from the previous Boos. Boos in this game are found in the Pumpkin Zone. A thrown Green Shell can defeat it. A new sub-species named Terekuribos, which are a species of undead Goombas, also appears in this game.

''Hotel Mario
Boos also appear in the game Hotel Mario, though exclusively under the name of Boo Buddies. There are two types of Boos in this game. One type stays visible and doesn't hurt Mario until transparency is achieved, at which they can harm the heroic plumber. The other type of Boo sticks with the more traditional attack method and turns invisible when looked at, and attacks Mario when his back is turned.

Yoshi
Boos make an appearance in Yoshi. They are enemies in the A Type part of the game, as well as the B Type. Boos are not main enemies in the game, they just make appearances throughout some parts of the game. Boo's sprite in the game, is like its sprite from Super Mario Bros. 3. Many of the other enemies' sprites also are similar to their sprites from Super Mario Bros. 3.

Yoshi's Safari
In Yoshi's Safari, Boos appear as enemies. They mainly appear in the Ghost Mansion, a level in the Dark Realm. A Big Boo serves as the boss for the level.

''Super Mario World 2: Yoshi's Island
Boos first appear chronologically as antagonists to Yoshi in Super Mario World 2: Yoshi's Island. They were first seen in World 2, which featured numerous ghastly creatures. They were underlings for Kamek, the head of the Magikoopas, who turned one Boo into Bigger Boo, which grew in size every time he was hit by an egg and served as a minor boss. The main boss of World 2 was 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 featured the Boo Blah, a spectacle Boo exclusive to this game. The only way to defeat Boos is by looking away and then make a egg bounce off a wall after it is thrown, hitting the ghost in the face.

''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. In this game, the normal Boo is called a Big Boo, despite not being an actual Big Boo. The Ghost Castle is also home to other Boo species: namely, the Boo Block, Blindfold Boo, and others. The stage, Yoshi Sewers, also has ghost platforms, along with a blue boo variant called a Boo Buddy.

''Yoshi's Universal Gravitation
Boos appear again in Yoshi's Universal Gravitation however in this game they are very rare enemies. In fact, there are only four missions that they appear in. They follow the same tactics as normal, they are in 3-D, and they retain their normal laugh.

''Yoshi's Island DS
Yoshi, again, comes into contact with Boos in Yoshi's Island DS. Here, they are commonly found in castles, along with other ghastly creatures. Again, they are working for Kamek. They attack the same as all Boos before, but like in Super Mario World 2: Yoshi's Island, they can only be defeated if Yoshi looks away, so he must bounce an egg off of the wall into their face to defeat them. A Boo-like mid-boss, named Hector the Reflector appears as well. The Boos' laughs are used in many games before. It is used for the boss Six-Face Sal, and even Baby Bowser.

''Super Mario RPG: Legend of the Seven Stars
Boos return during the events of Super Mario RPG: Legend of the Seven Stars. However, once again, the English translation erroneously calls them "The Big Boo" (Always "Teresa" rather than "Atomic Teresa" in Japan). These Boos, like other Boos before them, hide behind their arms when stared at. However, some of The Big Boos teleport around the room, attempting to scare Mario and his friends. The Big Boos live in Kero Sewers along with many other ghouls, including Hobgoblins and Shadows. Often, these three undead monsters will assist each other in battle. Strangely enough, Big Boos have no physical defense, making them extremely weak enemies (even a Goomba has three defense points). However, The Big Boos make up for their lack of defense with high evasion, meaning that most attacks against a The Big Boo will miss. In battle, The Big Boos command powerful lighting magic, including the attacks Lightning Orb and Bolt. The Big Boos also know the special attack Scream, which cuts a party member's attack and defense in half. When not using magic, a The Big Boo will 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 Li'l Boos, which are the same size as normal Boos 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.

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 Luigi's Engine Room. Whenever the player travels in a Warp Pipe, they approach a Boo. After the board is completed a Boo, Koopa, and a Toad, along with the two runner-ups surround the victor and congratulate them.

Mario Party 2
Again, Boos make minor appearances in Mario Party 2. When a player obtains a Boo Bell, a rare item, they 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. This item could also be purchased by a Koopa Kid. The Boo Bell is replaced in Mario Party 4 by Boo's Crystal Ball. Boos also appear frequently on the board, Horror Land.

Mario Party 3
Boos also appear in Mario Party 3. They are not major characters in this game, they are among the Duel Partners in the Duel Mode Partners. Its partner is Yoshi and it is able to counterattack the attacker's move for equal damage. They also return along with the Boo Bell.

Mario Party 4
In Mario Party 4, a Boo plays a major role as the host for Boo's Haunted Bash. This boo has a whole new look with a wizard's cape Like the other hosts in the game, it is the character to reward to player with a star. Multiple Boos also appear on this board as background characters. 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 other Boos own the Boo House, allowing players to steal stars and coins from their opponents. Boo's Crystal Ball has the same effect as the Boo house. Two sidegames involving Boos requires a Mini Mushroom. One of them has the player pressing one of the keys of the Horn of Penalty 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 sidegame 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; he targets all players instead of one. Boo is also the fourth host of the Reversal of Fortune, who oversees what is given. Also, a Boo is an unlockable, playable character in the stage, Beach Volley Folley.

Mario Party 5
Mario Party 5 marks the first game in the Mario Party series where a Boo is a playable character in Party Mode. It is one of the unlockable 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 background appearances.

Mario Party 6
Boos reappear as playable characters in Mario Party 6. In this game, it is a starting character. 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. Red Boos also appear two boards, Towering Treetop and Castaway Bay. This game also marks the third appearance of Red Boos in the Mario Party series.

Mario Party 7
Mario Party 7 marks the third Mario Party game where Boo is playable. It also marks Dry Bones's first playable appearance, who is Boo's partner throughout the game. Red Boos, again, 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.

Mario Party 8
Mario Party 8, marks the latest game where Boo is a playable character. Boo's partner, again, is Dry Bones. 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 this board, Boos appear in the background. One owns an Item Shop.

Mario Party Advance
Boos appear in Mario Party Advance as supporting characters. They appear in a few minigames, including Boo-Bye. They also appear in the Boo Cemetery where they are main characters in the quest, True-Blue Boo. This is a mystery quest. They also appear in the Horror Condo in the quest Condo of Mystery!.

Mario Party DS
Boo is not a playable character in Mario Party DS and played no part in board play, but appears as an unlockable figure, also appearing in the mini-games Boo Tag, and Peek-a-Boo, where a lot of different Boos appear in outfits, such as hats.

Mario Tennis series
A Boo appears in Mario Tennis for the Nintendo 64. It is classified as a tricky character. The only other tricky character is Paratroopa. Boo also appears in Mario Power Tennis where it is a playable character. When it wins a championship, Mario and Luigi would come out with the trophy and Boo would be missing. They look around and then the trophy would start to float. Boo then appear unders it and Mario and Luigi are relieved. Then they start floating and the air is full of Boos who start flying around. Then the main Boo flies up to the screen and holds the trophy. Boo's taunt is to wave its racket while laughing. Boo's offensive power shot is the Boo Blast and its defensive power shot is the Boo Brigade Return.

Mario Golf series
A Boo makes a couple of appearances in the Mario Golf series. It first appears in Mario Golf for the Nintendo 64. Boo is one Mario's Power Star Holes for Hole 2. Also, Boos appear in one of the courses, Boo Valley. Boo is one of the unlockable characters in Mario Golf: Toadstool Tour, the others being Bowser Jr., Shadow Mario, and Petey Piranha. Boos also appear in one of the courses, Bowser Badlands. Strangely, Boo hits right-handed in this game, where in the Mario Baseball series, it hits left-handed.

''Paper Mario
The Boo's Mansion in Paper Mario for the Nintendo 64 is a bigger version of the SNES Super Mario World Ghost Houses, which has many puzzles involving Boos in it. The only difference, is that these Boos are kind, but tricky Boos. After solving these puzzles, Lady Bow, the princess of the Boos, joins Mario's party, in order to destroy Tubba Blubba, who had been terrorizing the native Boos, by having them as a snack. One certain Boo he ate was Stanley. Mario helps Lady Bow in order to get the Star Spirit she has in her possession. In Paper Mario: The Thousand-Year Door, Bow and Bootler are seen on vacation in Poshley Heights after Mario and his teammates defeat the Shadow Queen.

''Paper Mario: The Thousand-Year Door
In the GameCube game Paper Mario: The Thousand-Year Door, the Boos live in a tower called Creepy Steeple. 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 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 Shroom. If Mario is wrong the Boo will give him one Coin. Upon returning 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 Sentinels in Tubba Blubba's Castle If Mario Spin Attacks them several times, they merge into the Atomic Boo. Once the Atomic Boo is defeated, Mario can fight Boos in other parts of the Steeple. Strangely enough, the original Creepy Steeple Boo sends a letter to Mario that thanks him for freeing his friends, despite the fact that he and his friends attacked him. He signs the letter "The Creepy Steeple Boo". More Boos can be found in the Pit of 100 Trials. The game also introduced a more powerful sub-species, the Dark Boo which can be found in Poshley Sanctum.

''Super Paper Mario
Boos return as enemies in Super Paper Mario. Additionally, the Arcade in Flipside houses a Boo themed shooting game. This game has the player shooting Boos (Both Normal, Dark and occasionally Big Boos) to score points. A Toad frequently appears to give power ups, as long as the player saves him from his Boo captor.

Mario Bros.
Boos make an appearance in the Super Mario All-Stars remake of Mario Bros.. Koopa Troopas and Spinies also appear in the remakes of Mario Bros., but not in the same remake as Boos. Boos also replace the green fireballs from the original Mario Bros..

Mario Clash
Boos make appearances in Mario Clash. They are among the nine enemies. Though Mario Clash is a new style of Mario Bros., Boos did not appear in Mario Bros.. In this game, Boos' objectives are to defeat Mario, but Mario is able to attack a Boo from the side.

''Luigi's Mansion
In Luigi's Mansion, Boos are the main antagonists. King Boo sent a letter to Luigi, stating that he had won a Mansion in a contest. However, Luigi did not enter any contest, but paid no attention, and headed off. Mario went on ahead, but get captures by the King of the Boos, King Boo. Luigi had to rescue his brother from the Boos, using E. Gadd's Poltergust 3000. Luigi manages to find his brother, stuck in a painting. He ends up having to battle King Boo in order to rescue Mario. King Boo sends them to the roof of the Mansion, and uses a Bowser suit to battle him. However, the suit's head could come off once a spikeball was thrown at him, and King Boo would float out, leaving him open for Luigi's Poltergust. After taking away all of his 500 HP, King Boo is turned into a painting, and Mario is restored back to his normal self. However, King Boo manages to escape by unknown means and reappears in several Mario games.

There are 51 Boos which Luigi must suck up in the Poltergust 3000. There are 50 regular Boos, 15 of them making up the portrait ghost Boolossus, with King Boo as the final Boo. When Luigi attacks them, they usually run away, but occasionally twirl into him to cause damage. See this section for more information about the individual Boos. It should also be noted that all of the 36 Boos, excluding King Boo and counting Boolossus as one Boo, have puns in their names.

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 can not do the same to their gigantic counterparts.

Mario Hoops 3-on-3
A Boo makes an appearance in Mario Hoops 3-on-3. It appears as an unlockable character. It is unlocked by beating the Flower Tourney on hard. Boo's special ability is the Thriller Dunk. This is performed by tapping a B-like shape twice. In the game, the Boo is classified as a tricky character. The other tricky characters are Paratroopa, Fly Guy, and Moogle. Boo is also one of many of the unlockable characters to not have a baller name.

Mario Sports Mix
Boos appear in Mario Sports Mix. They appear as the only members of the crowd in Luigi's Mansion. Their appearances are in Basketball and Volleyball matches. They laughs can be heard. The Boos circle around the court.

''Mario & Luigi: Superstar Saga
In Mario & Luigi: Superstar Saga, Boos are enemies that only appear in Bowser's Castle. Outside of the 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 outside battle. In battle, they fly up into the air, and fall back down into the Mario Bros., and even prohibit the use of certain moves. These Boos are unknowingly aiding Bowletta, thinking she is the actual Bowser.

''Mario & Luigi: Partners in Time
During the events of Mario & Luigi: Partners in Time, Boos appear in Bowser's Castle of the past. Mario, Luigi, Baby Mario, and Baby Luigi meet a lot of them while trying to reach the end of Baby Bowser's Castle. In the field, Boos attack the same way as they did in Mario & Luigi: Superstar Saga, but in-battle they fight differently, and have significantly decreased defense. They cover their faces, but when they start to attack, the Boo would take one of its hands off one of its eyes, showing who it is about to attack. If it shows its right eye, it will attack Mario, but if it shows its left eye, it is attacking Luigi. Then it would appear from behind, and charge towards one of the Mario Bros.. However, this could easily be countered with a jump. They also appeared during the battle with Sunnycide. After the Mario Bros. flip the egg monster over, Sunnycide could summon a Boo to attack Mario or Luigi. Dark Boos also return in the game, and were found in the Gritzy Caves.

''Mario & Luigi: Bowser's Inside Story
Boos make a reappearance in Mario & Luigi: Bowser's Inside Story. They appear in Bowser's Castle, after being brainwashed by Fawful, and they also help many of the former minions of Bowser push the Fawful statue against the power-upped Bowser. In addition, a Boo appears whenever Bowser gets a level up. The Boo (just like the Lakitu in Mario's or Luigi's level up screen) holds the circle for getting a bonus upgrade for the stat of the players choice.

Yikk, a ghost who appears in the same game at the Tower of Yikk, explains that he researches Boos. He even built a machine to visualize Boo transparency waves before he passed away.

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 love Fawful, due to the brainwashing that was put on the minions.

''Mario vs. Donkey Kong
A Boo appears once in Mario vs. Donkey Kong at the Spooky House. It acts just like its former battle strategy, with it hiding when Mario looks at it and only attacking when its back is turned. It will spit its tongue out at Mario if he is about to lose a life.

''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 2000 points. They occasionally will disappear and reappear to another spot in the area.

''Super Princess Peach
Boos appear in Princess Peach's first starring game, Super Princess Peach. They act as normal Boos, hiding their face when Peach looked, and attacking 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.

Super Smash Bros. Brawl
As well as appearing as a trophy in Super Smash Bros. Brawl, Boos make cameos in the Luigi's Mansion stage. When a part of the mansion is knocked down, Boos are seen flying out.

Appearance
Though their specifics change from game to game, Boos are usually bashful, cowardly, spherical ghosts. Although they are typically white in color there are sub-species of the Boo race which appear in different colors, such as pink. From Luigi's Mansion onward, it became common to picture Boos sticking out their tongues. Since Super Mario 64, Boos have been portrayed with a unique, high-pitched laugh. In actuality, this laugh is the same as Bowser's, sped up several times. However, Boos got a new laugh starting in the Hide and Boo Seek mini game, being more of a haunting laugh than before. Although most species of Boo will cover their faces and become intangible when looked at, they will often sneak behind their victim and strike when their back is turned. Due to their ghostly abilities, Boos are generally invulnerable, and cannot be harmed by ordinary means of attack. While this is true, they are not invincible, and are especially vulnerable to the light. If they are exposed to a source of light, Boos are usually weakened, and in some cases they may even perish. Usually, they can also have other weaknesses. Because of their intolerance to the light, Boos will often hide if they are trapped in lit rooms. While the ghosts generally appear to be more afraid of their victims than their victim is of them, this is not always the case. Some Boos have absolutely no problem meeting their victim's gaze, and will even try to attack. Boos tend to have a taste for the fine arts, as seen in Paper Mario and Mario Party 4. The best way to defeat a Boo is to sneak behind it so it cannot see the player and disappear, or to set a trap for the Boo while the player's back is turned (ie: using an item, or in Super Paper Mario, a Pixl).

Boos are often characterized by their sub-species; despite their similarities in appearance and attack manner. Boo species tend to wildly differ in size, with some such as Boo Buddies being miniature, while others such as the Big Boos boast gigantic size.

In Luigi's Mansion, Professor E. Gadd notes that Boos have mysterious powers that increase when they gather together in large groups. While it is difficult to stop them, they can be weakened if one is able to defeat members of the group.

Boos have few predators, their only known threat being a Clubba named Tubba Blubba. This is first seen in Paper Mario, when he began devouring Boos; this, however, may have been his revenge for the countless times the ghosts scared him.

Tools

 * Boo's Sheet - ''Paper Mario: The Thousand-Year Door
 * Fright Bomb - ''Super Mario RPG: Legend of the Seven Stars
 * Boo Bell - ''Mario Party 2
 * Boo's Crystal Ball - ''Mario Party 4

Home
Boos typically make their homes in dark forests, such as the Forever Forest and Boo Woods, and tend to be most commonly found in older buildings such as mansions, castles, and Ghost Houses. Although most of them live in such dwellings, they also seem to enjoy wastelands. One of the only known Boo villages lies in Gusty Gulch. They are typically found in groups because their fears make them find strength in big numbers.

Allegiance
Though most Boos tend to side with King Boo, they seem to, for the most part, actually stand as neutral. For example, Boos are by now a common enemy in most side-scrolling games; however, in the Paper Mario series and now increasingly in the multiplayer games, Boos have been seen to take the side of the Mushroom Kingdom. Lady Bow, in fact, helped Mario save the kingdom in Paper Mario. In another example, the Boos in the Creepy Steeple from Paper Mario: The Thousand-Year Door attack Mario initially, but later in the game Mario is sent a friendly letter from one of them. King Boo, on the other hand, has several times been shown to wish nothing but terrible things for Luigi (but this could be accredited to Luigi being easily scared, making him a prime target for most Boo antics).

Lil' Boo's Stats, ''Super Mario RPG: Legend of the Seven Stars

 * HP 66
 * Attack 120
 * Defense 20
 * Magic Attack 74
 * Magic Defense 120

The Big Boo's Stats, ''Super Mario RPG: Legend of the Seven Stars

 * HP 43
 * Attack 18
 * Defense 0
 * Magic Attack 18
 * Magic Defense 24

''Mario Superstar Baseball Information

 * Type: Technique
 * Starting Team Captain: Wario
 * Status: Player
 * Stats:
 * Batting: 3/10
 * Pitching: 8/10
 * Fielding: 2/10
 * Running: 4/10
 * Player Profile:
 * Strength: Pitching
 * Special Talents: Super Jump
 * Trajectory:
 * Field: Center
 * Height: Normal
 * Star Pitch: Curveball
 * Star Swing: Center
 * Sweet Spot: The Boo face on the bat
 * Compatible Relationships: Wario, Magikoopa, King Boo
 * Bio: "Bowser's underling ghost. Behind the scary face lies a very shy soul. Look most Boos in the eyes and they'll cover their faces...but turn around and they'll attack you! Boos confuse their enemies by flickering in and out of the visible realm, appearing at inconvenient times."

''Mario Hoops 3-on-3

 * Type: Tricky
 * Special Shot: Thriller Dunk
 * Letter to Tap: B

Mario Party DS

 * Trophy: This ghostly creature is a common sight. Do you think he's a nice guy? Ask him. He's right behind you.

Mario Party 7 Info

 * Partner: Dry Bones
 * Special Orb: Magic/Surprise

Trivia

 * Boo's Mario Strikers Charged Football outfits resembles the Spooky Speedster's outfit.
 * The manual for Mario Kart DS refers to the item Boo as "Boo Hoo".
 * Creator Shigeru Miyamoto got the idea for Boo from the wife of his co-worker and close friend Takashi Tezuka, as she is shy but one day got very angry at him for coming home late from work.
 * Boo's old laugh is just a sped up version of Bowser's laugh with echoes added.