When one's prolapsed anus becomes both sentient and shredded into a sort of multi tentacle-esque shape. Wiping becomes a problem. If it isn't a "bloody" mess, it is digesting Boba Fett.
Dude 1: Hey did you see the movie recently with anal dentata?
Dude 2: Yea dude, that was one heck of a sarlacc anus.