Boo Balloon

A Boo Balloon, also known as a Blue Boo, is a Boo in the shape of a blue balloon in Super Mario World 2: Yoshi's Island. They race about the screen, trying to deal damage to Yoshi. They will inflate when hit with a Yoshi Egg. After three hits, they will explode, yielding coins or sometimes a ! Switch.

Trivia

 * The Nintendo Power SNES guide erroneously lists Blue Boos as separate from Boo Balloons, with Blue Boos exclusively appearing in Bigger Boo's Fort; however, they are the same enemy, and as such also appear in Don't Look Back!