Continuity mistake: In the scene where Frank Morris arrives at Alcatraz, he has to take all his clothes off for a routine check. When the guards escort him to his cell you can see him wearing a pair of white boxers, but in the next scene (still walking) he is naked again and when placed into his cell you can see him wearing a pair of pants. (00:06:15)
Continuity mistake: When Clint and some other prisoners are showering, one of the prisoners approaches Clint, who quickly gives him three punches in the stomach and shoves a bar of soap into his mouth. The soap falls out of his mouth before he falls to the ground, but once on the ground, he has the soap in his mouth again.