Monsterex is created when Krang attempts to blast the Ninja Turtles back into baby turtles with a mutagen ray and instead hits their television. The ray interacts with the monster movie they were watching and creates the strange patchwork monster out of thin air. Though the turtles attempt to stop this threat before it can begin, Monsterex proves too strong for them and escapes. The turtles follow in pursuit and with the aid of Bookwurm, head to the Magic Castle amusement park in New Jersey where they suspect the monster will be.