The Green Alien is a big alien and a one-time villian in Robotboy. His first Appearance was in the episode Aunty Gravitee. He doesn't speak and is only seen for a brief moment when he is getting into a fight in the space bar where Aunty Gravitee held her freakshow starring Gus. In Udder Madness he wants to attack and conquer the planet earth. Somehow he knows about Robotboy and realizes that he is the only one that can stop him. So the Green Alien send out his minions to kidnap Robotboy so that he can destroy him.