The Cave Monster was a monster who made a cameo appearance in the episode: Your Shoe's Untied. He ate SpongeBob after SpongeBob asked him if he knew how to tie his shoe. In the monster's mouth, SpongeBob asked a skeleton if he knew how to tie his shoes. This is the only episode that it appears in.
The monster is green, has various eyes and a very long tongue and sharp teeth. It lives in a cave.