Boo

Boos are recurring enemies in the Mario series. They are little ghosts who were introduced in Super Mario Bros. 3 as enemies, and since then have shown as a playable character in many Mario games. There have been many variations of Boos introduced throughout Mario's adventures. These include King Boo, Pink Boo, Boolossus, Bomb Boo and Big Boo.

Games
Boo has appeared throughout the entire Mario Party series. In the first four games Boo would steal coins (or even Stars) for the player, but soon became playable in Mario Party 5 for the GameCube. In a few of the Mario Kart series games, Boo was an item that wouldn't only make the player invisible, but but would allow them to steal an item from another character. King Boo was an unlockable character in Mario Kart: Double Dash!! for the GameCube, and Mario Kart Wii for the Wii. In Mario Golf: Toadstool Tour for the GameCube, Boo was an unlockable character, and it cold be unlocked by collecting fifty birdie badges. Boo was also playable in both Mario Tennis and Mario Power Tennis. Soon Boo was once again an enemy in the GameCube game, Luigi's Mansion. Then Boo appeared again as a playable character in Mario Hoops: 3-on-3 for the Nintendo DS and a team member in Mario Strikers: Charged for the Wii. The Boo was finally another enemy in the Wii game Super Mario Galaxy, and was a playable character Mario Super Sluggers, along with King Boo. He also appeared as a burger king toy.

Mario Kart DS
Boo appears in the Luigi's Mansion track in the stage floating around the scenery but not effecting gameplay.

Item
Boo is also available in the same game as an item that turns the driver invisible for a moment.