Jeffrey the Jellyfish first appears in the episode, "I'm Your Biggest Fanatic."
Jeffrey is 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.
Patrick chases him 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 that SpongeBob
and Mr. Krabs
go to to teach SpongeBob how to drive.