Aric the alien returns to Earth to help Richard Bickerstaff save the world from an invasion of Dwilbs, pollution-loving aliens who want to turn the planet into a toxic theme park.
Two days after Marvin sees a glowing green thing like a flying birthday cake in the night sky, his third-grade class is joined by a mysterious new boy with peculiar behavior.
Finding an intergalactic special agent in his cereal box, Richard joins the extraterrestrial in a fight to save Earth from the Dranes, one of whom is masquerading as a student in Richard's class.