Sleepy Boos are a Boo variant that appear in Super Mario Sunshine. Encountered in Hotel Delfino, these ghosts appear similar to regular Boos, but are constantly asleep. Their eyes are always closed and drool can be seen dangling from their mouths.
Sleepy Boos are immobile and will block Mario from entering parts of Hotel Delfino. Mario cannot defeat them on his own as neither his jumps nor the F.L.U.D.D. have any effect on Sleepy Boos. However, if Mario is riding a Yoshi, the Yoshi can grab the Boo with its tongue and eat it, thus clearing the way for Mario to pass through.