Mr. Peabody is the smartest being in the world. He was the main protagonist of the film, but he became more of a half deuteragonist/half supporting protagonist. He is voiced by Ty Burrell.
As a pup, Peabody was different from other dogs, being incredibly smart, and more interested in intellectual pursuits than the usual tricks of regular dogs, like playing fetch, which he called an "exercise in futility". As a result, no kids wanted to adopt him, leaving him lonely. Without a human family, Peabody devoted himself to the pursuit of knowledge and became active in many fields such as science and athletics, went on to graduate with top honors at Harvard (Vale-dog-torian), experimented with new methods of alternative fuel, and invented things like the fist-bump, planking, autotune, and Zumba.
One rainy day, as he was walking down the street, he heard crying from a nearby alley, and investigated, discovering an infant abandoned in a cardboard box, with only a blanket, and a paper with a name pinned to it, "Sherman".
Remembering his own childhood, and wanting to give the boy something he never had as a pup, a home and family, Peabody decided to adopt Sherman.
Mr. Peabody, as noted, is smarter than any living being on Earth. He is devoted to Sherman and has achomplished tons of things in life including inventing zumba, the fist bump, and winning the Nobel prize many times. He looks out for Sherman and does not want bad things to happen to him. In the show, Peabody was snobby and treated Sherman like a pet and an underling than a son.
- Mr. Peabody is similar to Cornelius from Disney animated film "Meet the Robinsons". Both are a genius, both invented time machine, and both have spectacles. Also, they both have a boy who does something harmful to the universe. Both are also orphans who never had a family growing up but eventually made one after they became successful.
- In contrast to the original series where he treated Sherman like an assistant and pet rather than a son, Mr. Peabody is shown throughout the film to be a loving, somewhat protective father who wants nothing more than to protect his son and care for him. Though, like the original series, he insists Sherman calls him Mr. Peabody rather than father (as to why remains unknown).
- In Russian version of the film he was voiced by a famous reporter Leonid Parfyonov.