As the Sharkboy and Lavagirl saga comes to a close, the heroic characters are faced with yet another crisis. Our heroes are beginning to settle down, and suddenly they notice something wierd in the sky. Dimension hopping beings called the Thumb Nation attack! Mr. Electrodad realizes his mistakes and joins Sharkboy, Lavagirl, and Max in order to save their realm. Mr. Electrodad creates a marvelous contraption allowing inter-dimensional travel. With this he is able to pull some unsuspecting characters into their realm to help fight the Thumb Nation. Who will the new characters be? Why the Spy kids and Pennywise of course!