The cartoons are about Peabody, who is the smartest being in existence. Peabody has accomplished many things in his life as a business magnate, inventor, scientist, Nobel laureate, gourmand, and two-time Olympic medalist. Peabody becomes sad and lonely and decides to adopt his own human son. In an alley, he meets Sherman (voiced by Walter Tetley), a bespectacled, red-haired boy. After saving Sherman from a group of bullies, Peabody discovers that Sherman is an orphan and decides to adopt him.
After a court appearance and a talk with the President and the government, Peabody becomes Sherman's new guardian. Mr. Peabody tells Sherman not to call him "Daddy" and to call him by his name, "Mr. Peabody", or, when speaking informally, "Peabody".
Believing that boys need running room, Peabody invents the WABAC time machine as a birthday gift for Sherman. Peabody makes some more adjustments, turning the WABAC into a "should-have-been machine". This causes past events to seem distorted and anachronistic and famous people to behave out of character. Each of the cartoons usually ends with Mr. Peabody making a bad pun.
