In an island world called Volcano Island, a trio of crabs, led by the Wise Old Crab and his two assistants are gathering around a ritual at Summoner's Rock to summon 'The Nine' heroes to defeat their ancient enemy, the Mawgu. However, the Mawgu breaks the circle of summoning, scattering the nine heroes across the island. SpongeBob SquarePants and Danny Phantom end up right where the Wise Old Crab is. He tells them that he has summoned them here and tells them that the Mawgu has escaped from his prison and is seeking vengeance against the island. The Mawgu has created a terrible ooze corrupting everything and everyone that it touches. However, according to the crabs' legends, the "Chosen Ones" can rescue everyone from the Mawgu Ooze and defeat the Mawgu.