Jeffrey wears a large mascot suit of a pink jellyfish. Instead of normal stingers, he has legs and knees, as shown when they are bent over while Patrick carries him away in a little wagon. His expression seems to change depending on the situation.
Role in series
"I'm Your Biggest Fanatic"
Patrick chases him because he wants to touch him. At the end of the episode, Patrick has him tied up in a wagon.
He appears in the background at the arcade where SpongeBob and Mr. Krabs go to, to teach SpongeBob how to drive.
He is visible in the background.
The Clam Prix
His name is seen in the game.
"Tutor Sauce" reveals that when the jellyfish convention is not happening, Jeffrey the Jellyfish works at an arcade.