Darwin is a chimpanzee who travels with the family and is a loyal companion to Eliza, and the secondary protagonist character of the series. He usually wears a tank top with horizontal blue and white stripes (which used to be Debbie's lucky tank top) and blue shorts. He speaks with a distinct upper-class British accent. He tries to be the voice of reason to Eliza, but Eliza rarely takes his advice.
Cautious by nature, he is almost always hesitant to follow her plans; in response, she accuses him of cowardice, once calling him a "crybaby in a tank-top" for his hesitancy. He was found by Eliza and was the first animal she ever talked to. His name is most likely reference to Charles Darwin who created the Theory of Evolution, though within the series Eliza gives him the name Darwin after Lenny Darwin, her cousin who looks like a monkey (who is never shown in the series).
