Not to be confused with the cousin Roscoe from Country Cousin.
Roscoe is the son of Al and the second cousin of Jon Arbuckle. He is smart for his age and, although seemingly polite, is secretly mischievous. He has his own lab with various inventions, including a robot and a rocket ship, both of which he uses to torment Garfield (who also gets blamed for accidents). Before leaving, Garfield gives Roscoe a taste of his own medicine by turning the robot on him.