Max is a lonely child who has created an imaginary world called Planet Drool, which is watched over by Sharkboy, a boy raised by sharks, and Lavagirl, who can produce fire and lava but can't touch objects without setting them on fire. His parents have almost no time for him and he is constantly bullied by the school bully Linus. One day, Linus steal's Max's journal and vandalizes it. After a tornado hits the school, Sharkboy and Lavagirl appear in the classroom and take Max to Planet Drool which is now in trouble because of the acts of Mr. Electric, the world's electrician now corrupt.