Revealing mistake: The scene in the sanitarium where Nash is given the insulin shot (usually done with a dummy retracting needle) you can see the tip of the needle slide along the skin as it is supposedly withdrawn. (01:19:05)
Revealing mistake: When Beverly is trying two throw herself down the stairs after she finds out she's pregnant, the padding on her behind to go down stairs shows through her pajamas. (00:30:40)
Revealing mistake: When Vercingétorix leaves the Romans to go to Gergovia there is a stone mason by the road carving what is probably a distance marker. The man's chisel is obviously not in contact with the stone - while he is banging it with the hammer it is waving around in the air. (00:17:00)
Revealing mistake: When Ali is in the rain on the pay phone at the motel it is a modern phone, not from the era they were trying to portray.