Continuity mistake: In the scene with Ali in training camp preparing for his first fight with Joe Frazier, he receives a call from Howard Cosell informing him that the Supreme Court had ruled in his favor regarding his refusal to enter the Vietnam draft. Ali could not have received this call while training for this fight with Frazier. The fight with Frazier took place on March 8, 1971. The Supreme Court did not even hear the case until April 19 and did not rule on it until June 28, 1971. In fact, one of the reasons the fight was scheduled in March and not later that year had to do with the pending Supreme Court case and the concerns that Ali would lose and sentenced to jail, which would have prevented the fight from happening.
Continuity mistake: When Malcom X visits Ali in his hotel room to tell him that he's been suspended from the Muslim Order, Ali is seen sitting down twice.
Continuity mistake: When Ali is driving and hears of Malcom X's death, he pulls over. There are back and forth shots of him from inside the car and from the front of the car. The shots from inside the car show sunlight on his face. The shots from outside the car show him in the shadow.
Factual error: The poem Ali quotes in the movie before the Frazier fight, "Ali comes out to meet Frazier, Frazier starts to retreat, If he goes back any further, He'll end up in a ringside seat..." was in fact the poem he used before the first Liston fight and began, "Clay comes out to meet Liston, Liston starts to retreat..." and ends with the lines, "Never did they think, When they laid down their money, That they would witness, The total eclipse of the Sonny". Poor effort.
Muhammad Ali: Hey, come on you big ugly bear, I'll turn you into a rug.
Sonny Liston: Keep talking! I'm gonna fuck you up.