The cashier is a character who only appears in the episode "Jailbreak!"
The cashier is a tall, light orange fish with black, fuzzy hair, and has light teal fins, and also has dark orange lips and eyelids. He also has buck teeth (much like SpongeBob's) and wore a white hat and a white shirt.
Role in episode
The Cashier was first seen reading a magazine called "Video Games" in the Grab-it Mart. He was scared into giving all of his money to the Purple Cellmate hoping not to see anymore of his "disgusting features."
The Cashier's role is pretty similar to Squidward's, as they both are cashiers and read magazines during their shifts.
Humorously, the Cashier was scared off by the Purple Cellmate whose face greatly resembled Squidward's at the time.