Boo Blah
From the Super Mario Wiki
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 he/she somehow bumped into them when they jump up. Stomping them stuns them for a little.
[edit] Trivia
- They could have been the inspiration for Luigi's Mansion's Ceiling Surprises, who are similar to them.
