Demon Jellyfish are a legion of genetically modified Jellyfish clones, which live a place known as the "Underwater" somewhere beneath the grounds of the Abyssal Zone in Club Jellyfish. They are and nearly all are criminally insane. They are the jellyfish version of Demon Penguins. They are stronger, faster, and heal more rapidly then normal Jellyfish, and can be distinguished from them by their color scheme. Demon Jellyfish want to take over Medusopolis. When they die, they become ocean foam.