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 appeared 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.

''Super Mario Bros. 3
In Super Mario Bros. 3, Boos appeared for the first time and were referred to as Boo Diddleys, a pun off the late former rock star Bo Diddley. However, future games referred to them only as Boos. The Boo would shield his face if Mario or Luigi looked at it, but would start chasing if Mario or Luigi looked away. Boos are unable to be defeated, unless the two were equipped with a Hammer Bro. Suit, Koopa shell, or Starman (Fireballs didn't affect Boos). The game also had Stretches, which were Boos with very long bodies that lived in the Fortresses throughout the kingdom.

''Super Mario World
In Super Mario World, there were Ghost Houses, which contained many Boos. These Boos retained their usual pattern of attack from Super Mario Bros. 3 and sometimes made faces at Mario or Luigi. The game also introduced a new sub-species of Boo, the Boo Buddy, which could take on numerous different forms. It also introduced 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 bunch 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 easily 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, but can be told apart from the fact they aren't spinning, while real coins do spin. It turns out that Hotel Delfino has numerous mysteries, including flipping floor tiles, a magic painting, and a flipping bookcase. Mario has a tough time trekking the mysterious hotel, and solving its many 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, which appears randomly, 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. They can be told apart because the fake Shadow Marios are very pale compared to the original. Their appearance had just one change, blue circles surrounding their black pupils. (Possibly due to the heat). Pink Boos also appear and can be turned into a platform if sprayed by F.L.U.D.D..

''Super Mario 64 DS
"You...can't...EAT...ghosts! Eee hee hee!"

- Boo

In Super Mario 64 DS, Boos kept 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.

''New Super Mario Bros.
Boos also appeared in New Super Mario Bros.. They were found mainly in Ghost Houses, scattered throughout the game as well as World 8-1. They appeared like they usually do, shy. The game also introduced 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 appeared in the 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 are 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. 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 reappeared from 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, 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 only 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.

Mario Kart series
In the Mario Kart series, the Boo is used as a very tactical item. 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 because King Boo is playable in those installments.

Boo was set to be playable in Mario Kart Wii, but was taken out of the final game in favor of King Boo, who had already appeared as a playable character in Mario Kart: Double Dash!!.

''Mario Super Sluggers
Boo made an appearance in Mario Super Sluggers. He is on Wario's team and can be unlocked in Wario City by finding him in between boxes and completing its challenge. 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 were once again featured in Super Mario Land 2: 6 Golden Coins. These Boos are relatively unchanged from the previous Boos. Boos in this game were found in the Pumpkin Zone. A thrown Green Shell is enough to finish it off for good. A new sub-species named Terekuribos, which are a species of undead Goombas, also appeared in this game. These boos walk like normal Goombas, but their weaknesses are those of Boos.

Super Mario Bros. film
In the live-action Super Mario Bros. movie, several Boos can be briefly seen surrounding the Valley of Bowser from Super Mario World on a television screen in the Boom Boom Bar.

''Hotel Mario
Boos also appeared 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.

''Super Mario World 2: Yoshi's Island
Boos first appeared 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 reappear 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 was called a Big Boo, despite not being an actual Big Boo. The Ghost Castle was also home to other Boo species: namely, the Boo Block, Blindfold Boo, and others. The stage, Yoshi Sewers, also had ghost platforms, along with a blue boo variant called a Boo Buddy.

''Yoshi's Universal Gravitation
Very, very few Boos were in Yoshi's Universal Gravitation. In fact, there are only four missions they exist in. They follow the same tactics as normal, they are in 3-D, and they retain their normal laugh.

''Yoshi's Island DS
Yoshi, yet again, came in contact with Boos in Yoshi's Island DS. Here, they are commonly found in castles, along with other ghastly creatures. They are, yet again, 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' laugh used in many games before is also 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 series
Boos also regularly appear in the Mario Party series. Boo started off as a non-playable character who helped to steal coins and stars from players when they passed by him. However, in Mario Party 5, Boo was a playable character in Party Mode. Mario Party 8 even featured King Boo's Haunted Hideaway as one of the boards; this was King Boo's first appearance in Mario Party. Boo's partner for Mario Party 3 was Yoshi, Koopa Kid in Mario Party 5 and Mario Party 6 and Dry Bones in Mario Party 7 and Mario Party 8. Boo was not a playable character in Mario Party DS and played no part in board play, but appeared as an unlockable figure, also appearing in the mini-games Boo Tag, and Peek-a-Boo. Boo might be Donkey Kong's replacement in the Mario Party Series.

Mario Party 4
In Mario Party 4, Boo plays a major role as one of the hosts of the Party Cube. Dressed in a magician's hat and vest, he controls the board Boo's Haunted Bash. Like the other hosts, he's the one who gives you the stars when playing on his board. Numerous other Boos play roles in the board too. One Boo controls the item shop. Another one owns the Mystery Train, but will only give a ride to the Boneyard if the Red Boo isn't there. This Boo doesn't actually get on it, but rather it runs on it's own. Two more Boos own the Boo House, which allows players to order a Boo to steal coins or a Star from another player by paying a certain amount of coins. 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. The stage Beach Volley Folley also has an unlockable Boo as a character.

Mario Tennis series
Boo appeared in Mario Power Tennis where he was a playable character. When he won a championship, Mario and Luigi would come out with the trophy and Boo would be missing. They'd look around and then the trophy would start floating. Boo would then appear under it and Mario and Luigi would be relieved. Then they would start floating and the air would be 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 his racket while laughing.

''Paper Mario
The Boo's Mansion in Paper Mario was a bigger version of the Super Mario World Ghost Houses, which had many puzzles involving Boos in it. The only difference, is that these Boos were kind Boos (yet, still a bit tricky). After solving these puzzles, Lady Bow, the princess of the Boos, joined 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 (Boo). Mario helped Lady Bow in order to get the Star Spirit she had 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 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.

''Luigi's Mansion
In Luigi's Mansion, the Boos were 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 got captured by the King of the Boos, King Boo. Luigi had to rescue his brother from the Boos, using E. Gadd's Poltergust 3000. Luigi managed to find his brother, stuck in a painting. He ended up having to battle King Boo in order to rescue Mario. King Boo sent them to the roof of the Mansion, and used 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 was turned into a painting, and Mario was restored back to his normal self. However, King Boo managed 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.

''Mario & Luigi: Superstar Saga
In Mario & Luigi: Superstar Saga, Boos were enemies that only appeared in Bowser's Castle. Outside battle, they would hover around, attacking Mario and Luigi when they are not looking. However, they would look away if Mario or Luigi made eye contact. The Boos also showed the ability to teleport outside battle. In battle, they would fly up into the air, and fall back down into the Mario Bros, and even prohibit the use of certain moves. These Boos were unknowingly aiding Bowletta, thinking she was the actual Bowser.

''Mario & Luigi: Partners in Time
During the events of Mario & Luigi: Partners in Time, Boos appeared in Bowser's Castle of the past. Mario, Luigi, Baby Mario, and Baby Luigi met a lot of them while trying to reach the end of Baby Bowser's Castle. In the field, Boos attacked the same way as they did in Mario & Luigi: Superstar Saga, but in-battle they fought differently, and had significantly decreased defense. They would 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 appeared once in Mario vs. Donkey Kong at the Spooky House. It acted just like its former battle strategy, with it hiding when Mario looks at it and only attacking when his 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 appeared in Princess Peach's first starring game, Super Princess Peach. They acted as normal Boos, hiding their face when Peach looked, and attacking when Peach had her back turned. However, there was an angry variety called the Mad Boo, which attacked the opposite way. They attacked when Peach looked at them ("losing their shyness"), 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.

The Appearance of a Boo
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.

In Paper Mario Goombario states that Boos must have strong facial muscles because of the way they surprise Toads.

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).

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

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

Gallery
For pictures, see this subject's gallery.

Trivia

 * Boo's Mario Strikers Charged Football outfits resembles the Spooky Speedster's outfit.
 * In Mario Kart Wii, an image of Boo and Dry Bones can be seen on a billboard on the Wii Bowser's Castle track.
 * In Sonic Adventure 2, there are enemies called Boom Boos and a boss called King Boom Boo which has a Boom Boo guarding an hourglass.
 * In the manual for Mario Kart DS, it calls the item Boo '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 name came from a word that is used when someone pops out of somewhere unexpected and scares another person, as well as from Bo Didley, a musician.
 * A very notable and interesting fact is that Boo's laugh is just a sped up version of Bowser's laugh with echoes added.