Jeffrey Jellyfish is a mascot for jellyfishing at the Bi-Annual Jellyfish Convention in the episode I'm Your Biggest Fanatic. Patrick is obsessed with him. On several occasions security guards had to chase Patrick away from the Jeffrey Jellyfish mascot because Patrick wanted to "touch" him.
Jeffrey Jellyfish is an ordinary Jellyfish but with more of a hot pink for skin color. He also has a smile and a face.
Patrick is his biggest fan and he wanted to touch him. He chased Jeffrey yelling "Wait, Jeffrey, I have to touch you!", and a police officer followed. In the end of I'm Your Biggest Fanatic, Patrick hitched him up to a wagon and carried him home, which is hypocritical because Patrick says "Hero worship is unhealthy, c'mon Jeffrey", tugging him along. It may be possible that the Police Officer catches up with Patrick and saves Jeffrey because we do not see him in other episodes.