•
Cayden Boyd as Max. An imaginative 10-year-old boy, known as the "day-dreamer" on Planet Drool. "At first he's dreaming all for himself; he wants Shark Boy and Lava Girl to take him away", Boyd said about the role. "I like that he's selfish in the beginning and he's not selfish in the end". Lautner's martial arts skills helped him to obtain the role of Sharkboy. "When I auditioned for the film, Robert Rodriguez, the director, didn't know that I had my martial arts [background], and while we were there in Austin, TX he saw a DVD of me and asked me to choreograph my own fight scenes", said Lautner. Lautner was the first to audition for the film, says Rodriguez, and was chosen immediately. • Taylor Dooley as Lavagirl. This role was cast after the two other main characters, Sharkboy and Max, had already been cast. •
David Arquette and
Kristin Davis play Max's parents. Max's father is an unemployed
writer. They are on the brink of a divorce. They mean well for Max but are unable to solve his problems. On Planet Drool, Max's parents appear as a pair of "Cookie
Giants" who live happily in the Land of Milk and Cookies. •
George Lopez as Mr. Electricidad, Mr. Electric, the voice of Tobor, and the voice of the Ice King. Mr. Electricidad is Max's teacher. Mr. Electric is Planet Drool's corrupt electrician. Tobor is an unfinished robot of Max that resided in the Dream Graveyard. The Ice King is the father of the Ice Princess. Rodriguez states that he kept asking Lopez to play additional characters. Lopez spent a total of two weeks working on the film. • Jacob Davich as Linus / Minus. He is a bully at Max's school and steals his Dream Journal. With it, he enters Max's dreamworld and, using the name "Minus" (a nickname bestowed by Mr. Electricidad for Linus' habit of disliked conduct) alters it to his version before ultimately befriending Max. •
Sasha Pieterse as Marissa Electricidad / Ice Princess. Marissa is the daughter of Mr. Electricidad, and at first, the only student who befriends Max. On Planet Drool, she appears as the Ice Princess, the ruler of the Ice Kingdom and keeper of the Crystal Heart, a necklace she wears that can freeze anything, including time. Director
Robert Rodriguez has an uncredited role voicing a shark, and his children, Rebel and Racer, portray Sharkboy at age five and age seven respectively. Rico Torres portrays Sharkboy's father. Marc Musso and Shane Graham play children at Max's school. ==Production==