He is a light green sea cucumber stylized to look like an actual cucumber and has a crown that is pale yellow with an orange outline attached to his head. He wears blue glasses along with brown colored shorts and has pink lips.
In "I'm Your Biggest Fanatic," he invites SpongeBob to go jellyfishing with the Jelly Spotters. He tricks SpongeBob into thinking he can join their club if he passes certain tests, simply so that he could humiliate and belittle him. This seems to be a habit of his, as many of his biggest fans have ended up stranded in a crevasse at Jellyfish Fields because of him.
However, all of Kevin's plans end up with him getting stung by jellyfish one too many times, causing his hatred for SpongeBob to grow. Finally he snaps and says SpongeBob is ready for the final test: use SpongeBob as live bait to catch a queen jellyfish. It is revealed the Jelly Spotters were using a robot queen jellyfish. Kevin and his friends then taunt and make fun of SpongeBob by calling him a "loser," but when a king jellyfish appears, it falls in love with the robotic queen and attacks them, Kevin proves to be a coward and admits that he was only in the club for the fashion.
When SpongeBob manages to ward away the king, Kevin was ruined when the Jelly Spotters ripped off his crown-like cranium and put it on SpongeBob. Although SpongeBob left the club, it's unlikely Kevin retained leadership of the club, as he lost the loyalty of his teammates.