In the original 1960s cartoon, Sherman is Peabody's sidekick and pet and therefore very obedient to Peabody. He is very curious and mischievous but always behaves very well due to Peabody's strict nature. He is rather simpleminded, often catching on slow to Peabody's plans during their time travel adventures. Sometimes, he can jump to conclusions.
Sherman is a very bright, mischevious, fun-loving, smart and ambitious boy who knows much about history due to his trips in the WABAC with his father and in fact takes after him in many aspects.
He also has a crush on Penny Peterson, his best friend and despises it when other boys flirt with her and is somewhat stubborn.