The Jellyspotters are an expert jellyfishing fraternity who first appear in the episode "I'm Your Biggest Fanatic." Most of them are anchovies who often speak in unison with their trademark "meep," with real dialogue thrown in.
Many fans admire them and take every bit of advice that their leader, Kevin the Sea Cucumber (Dee Bradley Baker), shares with them. One of their biggest fans is SpongeBob. In the episode they appear in, they are revealed to be less than what everyone thinks they are. Kevin, taking advantage of SpongeBob's obsessive need to join the club, takes him out to Jellyfish Fields to haze him. These gags ironically prove to be less than successful, as SpongeBob excels at every "test" and even calms a King Jellyfish after Kevin inadvertently antagonizes one.
Kevin and the Jellyspotters show their true incompetence in this incident, with SpongeBob easily saving them from painful electrocution, and was admitted into the club after winning the admiration of Kevin's gang. Kevin was replaced with SpongeBob, who quit though, realizing jellyfishing was all about the sport, not about Kevin. The club's only known members were five anchovies and Kevin. According to the latter, many tried to join the club, but were rejected.
The group is comprised of mostly, and now, possibly, just anchovies.
The only known former member is Kevin C. Cucumber. He was the leader until SpongeBob saved the Jellyspotters and they kicked him out.
The only known potential member is SpongeBob SquarePants. He was offered the position of the leader, but he turned them down.
All tests to join the Jellyspotters were created by Kevin, although he never intended to actually let anyone join, he just wanted to watch his crazed fans get stung and humiliated.
Catch a jellyfish
Catch two jellyfish at once
Catch 20 jellyfish at once
Let jellyfish lick jelly off one's face
Catch a jellyfish, walking on your hands
Catch a jellyfish, blindfolded
(Several other tests, presumably catching jellyfish in other unusual ways, possibly one could be catching a jellyfish without a net)
Assist in capture of a queen jellyfish. (Involves being tied up as bait, and using a queen jellyfish caller, a Kazoo that exclaims "Loser" to attract one. However it's all a setup, as the Queen jellyfish is a mechanical jellyfish, piloted by Kevin, to zap his fans and chase them into a chasm, where many previous fans still remain, as he's used it many times)
All of Kevin's friends were voiced by Rodger Bumpass, the same English-language voice actor of Squidward and Professor Membrane from Invader Zim.