Peabody's Improbable History features a talking dog historian and time traveler, Mr. Peabody and his pet boy Sherman. The duo would venture into their time machine aptly named "The Wayback Machine" and visit historic places and events only to discover that their assistance was necessary to make history turn out according to the history books. Each episode would end with Mr. Peabody delivering an atrocious pun, much to the chagrin of the audience and Sherman.

The Wayback Machine as depicted at the beginning of each episode is a monstrous contraption taking up an entire wall of Mr. Peabody's den. After setting the dials for the desired year, Peabody and Sherman would be seen entering a chamber and then be transported to their location.

The Wayback Machine serves its purpose as a simple plot device to transport our two characters to the required destination.  Curiously enough, in all the episodes they are never shown returning to the present. Presumably, the Wayback Machine has some sort of automatic retrieval device that returns them to the present after some duration, but this is all idle speculation.

Produced as a filler segment for Jay Ward's Rocky and Bullwinkle series beginning in 1959, Peabody's Improbable History, the Peabody cartoons are well remembered by the generation that first watched them. "Set the Wayback Machine" has become a familiar phrase for recalling times gone by.

Peabody and Sherman starred in an astounding 91 episodes of Peabody's Improbable History over the course of its initial five-year run. The series enjoyed continued longevity as it was repackaged as part of several other animated variety shows during the late 1960s and early 1970s and in reruns after that.

As with much of Jay Ward's efforts the series works on numerous levels offering something for both the child and adult audience alike. Peabody's groaner of a pun at the conclusion of the episodes was always worth waiting for.

As for the time travel aspects of the show, it always appeared that after arriving on the scene Peabody and Sherman would discover that the reality of the past was not what the history books had made it out to be. Mr. Peabody and Sherman always took upon themselves to get involved and set things right in order to keep history on the right track.

Despite appearances, it could be argued that the opposite was true and that the past was immutable, that is not open to intervention and change. The reason the history books are written the way they are directly because of Peabody and Sherman's involvement. The paradox being that they have influence history already, before they realize they must intervene.

An example is the episode featuring William Tell, where the hapless Tell is nearly blind without his spectacles and doomed to kill his son in the process of shooting the apple from his head. Peabody and Sherman intervene trying to assist Tell in improving his aim, only to discover they will have to cheat. After William Tell successfully shoots the apple off of his son's head, Peabody reveals that he had hid a powerful magnet in the core of the apple that caused the arrow to hit its target without fail. Peabody concludes his history lesson with his groaner of a pun saying something to the effect that Tell's eyesight was so bad that they eventually named a type of eye problem after him - Television. All together now --- GROAN!