Jack M. Crazyfish is a big purple fish that is the main antagonist in the episode "Blackened Sponge." He is a fish in SpongeBob's dreams, but actually a real person who lives in Bikini Bottom. SpongeBob gets a black eye from trying to take the lid off his toothpaste but he punches himself in the eyeball but makes up a story that he got it from fighting Crazyfish. Crazyfish then comes to the Krusty Krab because he heard that SpongeBob makes great Krabby Patties, and he's hungry for one. He also makes a cameo appearance in "20,000 Patties Under the Sea"; although he just throws rocks at Plankton.
Jack is a fish with a very big body. He wears a brown suit and a yellow shirt underneath. He has a big mustache and a small green top hat on his head. His skin is light purple.
His voice is different on his first appearance ("Blackened Sponge") from his second appearance ("20,000 Patties Under the Sea").
Ever since his first appearance in "Blackened Sponge," he has become a cameo character in "20,000 Patties Under the Sea."
When he walks into the Krusty Krab, SpongeBob says "He's real." Although when SpongeBob tells Sandy about him, She seems to know about him. One possible reason is that she may have seen or met Crazyfish.
Jack M. Crazyfish has never appeared outside of the fifth season.