Deliberate mistake: While Donnie is training at Front Street Gym, when Rocky repeats, "One step at a time, one punch at a time, one round at a time," the closeup of two children watching from outside the ring is a flipped shot, note the backwards Nike swoosh logo and Everlast ring rope spacer. (00:53:05)
Deliberate mistake: At about 1:49 in the movie, Glass is awakened by an attacking force of Arikara, and he fires his single-shot, muzzle-loading flintlock pistol at the nearest one coming at him. Then he runs to his nearby horse and flees, turning back to fire the gun a second time immediately. No reloading and no second gun on his person. It never leaves his hand; he's whacking the horse's rump with it to goad it on as soon as he jumps on it. And then he fires that same gun another time in a matter of seconds. (01:40:00)