Will Smith actually turned down the role of Ali. He relented after Ali called Smith and asked him to take the role, because he was the only one as good looking as him that could play the role.
Will Smith and director Michael Mann offered to put up their salaries in case the film went over-budget.
During the opening weigh-in scene, as the shoot was running into the early morning hours, Jon Voight took extras cell phones and called their homes. Some people got voice mails saying "This is Jon Voight. Don't worry, your husband is still on set working, not out in a bar, or chasing girls."