The Purple Cellmate is mainly a large, male, purple fish. He, along with the Whale Cellmate, appears to be the strongest of the group.
The Purple Cellmate was first seen taking food from Plankton (not knowing who he was at the time). The Purple Cellmate, along with Reggie, then beat up the Light Blue Cellmate for thinking that he was calling himself Plankton. The Purple Cellmate revealed that he and the others are big fans of Plankton because his chum is great in pulling off crimes. The Purple Cellmate then assists Plankton in breaking out of jail and breaking into the Krusty Krab. However, the Purple Cellmate, along with the others, were soon arrested at the end.
The Purple Cellmate has more lines in "Jailbreak!" than any other of Plankton's Cellmates.
The Purple Cellmate used chum to make himself look like Squidward.