Chuck is a 24-year-old identical twin who always stays with his twin brother Leon.
Chuck has a faux Scandinavian accent and a snooty attitude. He became a running gag along with Leon, having several odd jobs such as being gym owners, running a client agency for clients who need help to break bad habits (in Rocko's case, nail biting), running a hair salon (Haute Coiffeur), and owning a café. Most, if not all, of these establishments are, by their own admissions, very exclusive (such as for people with "an exclusive amount of cash", as was the case in the episode Tooth and Nail). He says that they once worked for a Czar (who resembled Heffer) in the fictional country of Balzak before immigrating to America. Chuck is voiced by Tom Kenny.
Chuck is naked most of the time. He is mostly green with blue eyelids, exactly like his brother Leon. Despite a chameleon, he and his brother look more akin to geckos.