One day, he invited SpongeBob to go jellyfishing with the Jelly Spotters. He tricked SpongeBob into thinking he could join their club if he passed 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 ended up with him getting stung by jellyfish one too many times, causing his hatred for SpongeBob to grow. Finally he snapped and said SpongeBob was ready for the final test: use SpongeBob as live bait to catch a queen jellyfish.
It was revealed the Jelly Spotters were using a robot queen jellyfish. Kevin and his friends then taunted and made fun of SpongeBob so badly by calling him a "loser," but when a king jellyfish fell in love with the robotic queen and attacked them, Kevin proved to be a coward and admitted that he was only in the club for the fashion. When SpongeBob managed 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. Since then, Kevin hasn't been in any other episode.
He doesn't seem to care about the well being of his fans, as he didn't care about SpongeBob punching himself, twice, or falling off a building.
Along with other fans of Kevin, he neglected them as well.
Kevin's "hat" is actually his tentacles. This is why he was in such pain when the Jelly Spotters forcefully removed it.