Other mistake: During the Baer and Braddock fight, when the camera angle is from far away, you can see that Braddock is not actually connecting with his punches on Baer. Yet Baer still reacts like he's been hit. This also true with Baer hitting Braddock when the camera is showing the fight from far away in the stands.
Other mistake: In the scene where Johnny Cash is seen beating his first wife, there are at least two shots from behind where the "tag" on Johnny's t-shirt can be seen. However, this visible tag is one of the new Hanes tag-less tees, which clearly was not available at that time.
Other mistake: During the end credits of the film, Thunder Monkey's real name is America Ferrera, best known for playing Ugly Betty. However, her name is misspelled as America Herrera.