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).
Darwin likes to live with indoor plumbing than in the wilds of the jungle. This too cautious individual is Eliza's best friend. Darwin met the Thornberrys as they were filming a show and became friends with Eliza. The two pals wanted to communicate with each other, but obviously, couldn't. It took a magic spell of an African shaman to enable Darwin and Eliza to talk, but they've been chatting to each other ever since. Darwin has adapted well to living with humans. He enjoys eating Cheese Munchies and loves the safety that the Commvee provides him from the dangers of the wild. Although Darwin is easily startled and usually very nervous about following Eliza on one of her adventures, he almost always goes along and has saved her life on numerous occasions. Even though Darwin is a chimpanzee, he is considered a valuable member of the Thornberry family.
Darwin has some gray fur as well as peach skin and a pair of white eyes with black pupils. He wears a sleeveless tank top with blue and white stripes and blue pants.
Darwin is often referred to as a monkey, but he is more like a chimpanzee.