Old Bluelip - Avoid him at all costs!
Old Bluelip is supposedly a giant, deadly blue lipped clam that first appeared in the episode Clams. It is notable for stealing Mr. Krabs ' millionth dollar, terribly freaking out Mr. Krabs. It gave it back to him only to take the rest of his body. This character, along with the whole episode is a reference to the Great White Sharks in the Jaws series.
RAWR!!!!
He is also seen in the movie, Clams (Film), but a different name.