Boos are enemies that appear in Ghost Houses in New Super Mario Bros. Wii. They first appear in World 3's Ghost House in World 3 (NSMB Wii). Boos are small enemies, half the size of Mario. When Mario faces them, they cover their faces. When Mario turns his back on them, they follow him. Boos glow in the dark. However, they don't give off much light. Well, not as much as a Glow Block. Boos only appear in Ghost Houses along with Big Boos and Circling Boo Buddies, their sub-species. Big Boos are bigger Boos, however, they play the same role as a Boo. Circling Boo Buddies are a large ring of Boos with different facial expressions than most other Boos and only one space between two Boos in the ring that the heroes can pass through. If Mario (or Luigi, Blue Toad or Yellow Toad) touches a Boo, he will lose a form or die at small form. Boos circle around the Ghost House on a world's map. Boos may also come in groups, making them harder to dodge. The only way to defeat Boos and Big Boos (and probably Circling Boo Buddies) in this game is to touch them while under the effects of a Starman. Boos also make appearances in Super Mario Galaxy and its sequel, Super Paper Mario, Mario Kart Wii, Mario Party 8, Super Smash Bros. Brawl, Mario Super Sluggers, Mario Strikers Charged Football, Mario & Sonic at the Olympic Games, Mario Sports Mix and in Mario Party 9. In Super Mario Galaxy, Boos appear as enemies. They appear usually in haunted galaxies such as the Ghostly Galaxy and the Deep Dark Galaxy, however, they also make appearances in the Bigmouth Galaxy and the Sand Spiral Galaxy. Here, they appear from pictures on walls or can be found in halls, etc. When Mario/Luigi near the enemies, they will follow them (if the heroes are not facing them), trying to bump into them. If the heroes do face the Boos, they cover their faces and turn transparent. In this game, Boos can only be defeated by bringing them into the a light (lights usually shine on the floors, so they should be easy to spot) or by pointing the light given off from a Green Shell at them (underwater only), meaning a Spin or jump on them will not take them out. However, Boos can be Spun to throw them around Mario or into a wall/object, however, this still does not defeat them, for the Boo will reappear (if thrown into a wall/object) and continue to chase Mario. When Mario has become Boo Mario (or Luigi has become Boo Luigi) after consuming a Boo Mushroom, Boos tend to find him attractive and will slowly follow their "love at first sight". Are they gonna get him?! Well, this probably shows that Boos are female, but this is unknown. If it hits Mario/Luigi in this form, they will lose their boo suit, however, they will not take damage. Boos can be found underwater in the Bigmouth Galaxy. All they do is swim back and forth, much like how Cheep-Cheeps do. These underwater Boos could only be defeated by pointing the light given off from a Green Shell at them, causing them to vanish and release a Coin. Most Boos release Coins when defeated, some are needed to be defeated to give Keys or even Power Stars. An individual Boo known as the Spooky Speedster can be raced to earn a Power Star if the heroes come in 1st place. The Spooky Speedster only makes an appearance in the Ghostly Galaxy and the Boo's Boneyard Galaxy. Also, a new sub-species of Boos, the Bomb Boo makes its first appearance. They are black Boos with yellow eyes that can be Spun in order to grab them. The player can then make Mario/Luigi Spin again to hammer toss the Bomb Boos into statues, enemies, and even Bouldergeist's body (they are needed to defeat Bouldergeist) to cause them to explode and destroy objects/defeat enemies. However, if held on too long, Bomb Boos explode, causing Mario/Luigi to take damage. However, if Mario/Luigi Spins when they flash red, they can toss the enemy, protecting themselves from taking damage. If a Bomb Boo explodes on Mario/Luigi or one of the heroes touches a regular Boo, they will lose on wedge of health from their Health Meter. Boos reappear in Super Mario Galaxy 2 behaving no different from the prequel. They appear in haunted galaxies such as the Haunty Halls Galaxy and the Boo Moon Galaxy. Underwater Boos also appear, and they can be found in the Battle Belt Galaxy and the Slimy Spring Galaxy. Bomb Boos also reappear, however, they only appear in the Boss Blitz Galaxy to aid Mario/Luigi in defeating Bouldergeist, who also reappears in SMG 2. Big Boos make their first appearance in a "Mario Galaxy" game in SMG 2, however they only appear in the Haunty Halls Galaxy's second mission "Sneaking Down the Creepy Corridor". The Spooky Speedster does not appear in Super Mario Galaxy 2, however. In Super Paper Mario, Boos are enemies. They will turn invisible if Mario faces them, but they will become visible if Mario does not face them and follow him. To defeat a Boo, the player must approach them from the back and then attack them. The Arcade in Flipside houses features a game where players must shoot Boos, Dark Boos, and occasionally Big Boos to score points. A Toad appears frequently and gives Power-Ups, as long as the player saves him from the Boo that is holding him (if Toad is shot, points are lost). In Mario Kart Wii, Boos are not items nor obstacles, however, they make appearances in the retro course, Ghost Valley 2. The Boos only laugh at the racers, but they will eventually disappear. They also make a cameo appearance in Bowser's Castle. At the end of the track, Boo's artwork from Mario Party 7 can be seen, as well as Dry Bones' artwork. In Mario Super Sluggers as a playable character. It is on Wario's team, the Wario Muscles. Boo can be unlocked in Wario City by finding it in between boxes and completing its challenge. Boo has the highest pitch in the game, only to be tied Princess Peach, however his other stats tend to be average or low. Boo has good chemistry with King Boo, Shy Guy, Magikoopa and Blooper. However, he has bad chemistry with Luigi, Baby Mario, and Baby Luigi. A new item known as Mini Boos makes an appearance in Mario Super Sluggers as well. When activated, Mini Boos turn the ball invisible for a short period of time. If used against a NPC (non-playable character), the player will stop moving until the Boos go away. If used when a special hit is being used, the Boos will do nothing. In Mario Party 8, the Boo makes its latest appearance as a playable character, currently. Once again, Boo's partner is Dry Bones. Red Boos, a red (or you can call them pink) sub-species of Boos, appear in some minigames such as Boo-ting Gallery. Mario Party 8 also marks the first appearance of King Boo in a Mario Party game. King Boo 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 10 coins. There are three rooms, two of which have a trap hole in them. If the player finds one of these rooms, some Red Boos will throw him or her in, causing them to start from the beginning of the board. When the player gets a star, King Boo will rearrange the mansion's rooms. Red Boos appear as the owners of the Candy Shops. In Mario Party 9, King Boo appears as the boss of Boo's Horror Castle. Regular Boos also appear on the board. When the player passes a portrait of a Boo, much like in Super Mario Galaxy and Super Mario Galaxy 2, a Boo will come out of the portrait and chase them. These Boos move three spaces after each turn, and if a Boo happens to catch up to the players (or if the players catch up to a Boo) the current captain will lose half or all of his/her Mini Stars. During King Boo's Puzzle Attack, whenever King Boo loses half of his health, he sends Boos to appear and attack the player. If the player's cursor touches a Boo, the player will become stunned temporarily. King Boo only sends one Boo at a time. In Mario Strikers Charged Football, Boos are sidekicks to the captains, along with Hammer Bros, Toads, Koopas, Birdos, Dry Bones, Monty Moles and Shy Guys. They appear with a helmet with the logo of their team captain on it. Boos are classified as playmakers, along with Toads. Their skillshot is Possess. Boos appear in Mario Sports Mix on the Luigi's Mansion stage where all they do is circle around the stage. They make appearances in Basketball and Volleyball matches and their laughs can be heard during the match on that stage. Mainly, they can be heard when the player gets a point. Last but not least, Boos appear in Super Smash Bros. Brawl as a Sticker and a Trophy. They also appear on the Luigi's Mansion stage. When a pillar holding part of the mansion up is destroyed, these enemies will fly out for a few seconds. The Sticker of a Boo is [Throwing] Attack +14, making characters throws a little more powerful. The Sticker can be used by anyone.
Boo's Trophy Description in SSBBA bashful ghost who draws near when your back is turned but shyly stops and disappears when you face it. Boos have been seen recently in activities like baseball and tennis, so it's thought that they may have conquered their fear of humans. Boos are also characterized by having a variety of different weaknesses between forms.
- The Boo's outfit from Mario Strikers Charged Football resembles that of what the Spooky Speedster wears in Super Mario Galaxy.