Recurring Enemies in The Mario Series - Boo

Boo

Boos, known as Teresa (テレサ?) in Japan, are spectral beings with beady eyes, long tongues, and sharp fangs. The first appearance of Boos was in Super Mario Bros. 3, where they appear under the name Boo Diddley, a pun on Bo Diddley. In Super Mario World, there are much larger variations of the Boo under the name of Big Boo. All Boos are ghostly creatures that are able to pass through solid matter. However, they are shy, and will cover their face with their arms if anyone looks at them. Conversely, in Super Princess Peach some Boos act the exact opposite, chasing after the player when looked at. In Luigi's Mansion, Boos, led by King Boo, act as the main antagonists. Boos appear as playable characters in various Mario spin-off games. In Super Mario Galaxy, Mario can transform into Boo Mario, where he can float and become transparent. Also in Galaxy is a variation of a Boo called a Bomb Boo that latches onto Mario when he spins and will revolve around him until it comes into contact with an object, where it will explode. The courtyard in Super Mario 64 is populated with Boos, one of which provides access to the Big Boo's Mansion. Boo also has a small appearance on a level in New Super Mario Bros. Although Boo is considered shy, it has made appearances as a playable character in games such as Mario Party 8, Mario Kart Wii, and Mario Tennis. Boo has also appeared in all of the games in the Mario RPG series, including the Mario and Luigi games, the Paper Mario series, and Super Mario RPG. In Super Mario 3D Land, Boos can appear as Tail Boos, with tanooki tails, or as regular Boos.

Takashi Tezuka's wife was the inspiration for Boos; like them, she is often shy, but once became very angry at him for spending too much time at work.

Boo ranked in the fifth slot on GameDaily's top 10 Nintendo characters that deserve their own games list. GameDaily also listed it as the seventh best Mario enemy, citing the difficulty involved in defeating or outrunning it.