Darwin is a brown male guinea pig with white fur from the top of his forehead all the way down to his belly. He is mainly the top guinea pig of Juarez, Blaster, and Rookie, also known as Hurley. He is shown adorable, brave, and loyal. At the pet shop, an old man commented on Darwin that he was "full of life." Even after Ben told Darwin that his family had abandoned him because he was "the runt of the litter," Darwin still believed that he, Blaster, and Juarez were more than just "balls of fur waiting for their next pellet." It is revealed that Darwin is good at riding a motorcycle from a video game he was playing. Nobody really knows if Darwin is interested in Juarez. Often at times, it is shown that Blaster can sometimes get jealous of Darwin.