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 jump up periodically. A large majority live inside Bigger Boo's fort along with other spirits and Boos. They are invincible, but are not a problem as they'd only hurt the player if they somehow bumped into them when they jump up. Stomping them stuns them for a little. 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, who 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.