Factual error: In the beginning of the movie, during Lewis Carol's visit to America, you can hear them playing the melody from the song "The Yankee Doodle Boy" written by James Cohan in 1904. This was 64 years after the events in the movie. In the ending credits they cite this as "Yankee Doodle Dandy" which was written many years before. But, that was not the melody that was being played.
Factual error: There are references to failures of novels by Dickens that were actually not written until after the events depicted in the film (e.g. Martin Chuzzlewit and Romney and Son).