Gloomius Maximus is the main adversary of Rolie Polie Olie: the Great Defender of Fun. He is a space robot who never had any fun in his life. For this, he intends to steal the fun from everyone. He also hates birthday parties (as he reveals when an invitation to Zowie Polie's third birthday party is accidentally sent to him).
Later, after Olie uses his Silly Bubble Ray on Gloomius with a lot of bubbles, he becomes nicer, and Zowie invites him to her birthday party, and he has fun with his minions and the others.
He is voiced by James Woods.