Darwin is a brown male guinea pig with white fur that extends from the top of his head to his belly. He is mostly Juarez, Blaster, and Rookie, also known as Hurleytop ,'s guinea pig. He is shown to be endearing, bold, and devoted. Darwin was described as "full of life" by an elderly man at the pet store. Darwin still felt that he, Blaster, and Juarez were more than just "balls of fur waiting for their next pellet" after Ben told him that his family had abandoned him because he was "the runt of the litter." Darwin's ability to ride a motorcycle is discovered through a computer game he was playing. Nobody knows whether Darwin is interested in Juarez or not.