Factual error: Young Dewey is seen driving a tractor near the beginning of the movie. The year is supposed to be 1946, but the tractor is a 1950's Ford.
Factual error: When Dewey's variety show on CBS is failing, he's told that they were beaten in the ratings in their time slot by The Incredible Hulk. The Incredible Hulk also aired on CBS, so it wouldn't have been in competition for ratings with Dewey's show.