Max (Boyd) has always been a dreamer. Finding it hard to make friends, he retreats into his own dreams of adventure with his favourite characters Sharkboy (Lautner) and Lavagirl (Dooley) and the planet Drool. This is a magical place where kids can have untold escapades and Sharkboy and Lavagirl live when they are not visiting Earth.

When Max tells the rest of his class about his heroes, he instantly becomes the joke of the class and the school bully Linus (Davich) see this as open season on Max and sets out to totally ruin him.

What none of them realise is that Sharkboy, Lavagirl and the planet Drool actually exist and Max’s heroes are heading to his school because they need his help in a very important mission.