Boo

Boos are ghost enemies from the Mario series of games, debuting in Super Mario Bros. 3 for the Nintendo Entertainment System. They made cameo appearances in The Legend of Zelda: Link's Awakening, where they guarded the Power Bracelet. They are killed by lighting the two torches and then swinging the sword at them, though the player could just let them run away.

Trivia

 * In the Mario games, Boos can not be killed, and hide when looked at. This is not the case for their Zelda appearance.