Boo Blah

A Boo Blah is a kind of ghost that appears in Super Mario World 2: Yoshi's Island. This creature sticks to the ceiling or the floor and jumps up periodically. A large majority lives inside Bigger Boo's Fort along with other spirits and Boos. They are generally invincible but are not a major threat, as they only hurt the player if they somehow make contact with him or her while jumping up. Stomping them stuns them for a brief period of time and by holding the jump button, Yoshi can bounce off them. They can be defeated by using a POW Block or a cloud item.

Trivia

 * They could have been the inspiration for Luigi's Mansion ' s Ceiling Surprises, which are similar to them.
 * They look incredibly similar to the Camo Goblin enemy that appears in the DX version of The Legend of Zelda: Link's Awakening.