A student based on the Invisible Man. Sid is the class clown and does various impersonations (implying that perhaps he and his name were inspired by Sid Caesar), in contrast to the idea of the "invisible" one of the class being unnoticed. Oddly, Sid, like many cartoon anthropomorphic animals, apparently does not wear pants, unless his pants are invisible as the rest of his wardrobe is not. Sid's parents are also talented impersonators as seen in the episode "Night of the Living Dad."