Revealing mistake: When Morgana's ship is being boarded, one of the Vikings features an arrow stuck in his body even as he boards. It is first (but not quite) kept out of sight by his shield, but when he enters the ship, he turns the shield away, and the arrow is suddenly visible. Somewhat hard to see by casual watching, so look carefully.
Revealing mistake: During the scene where the Vikings are attacking the castle, a soldier gets an arrow straight across the neck side on. Given that the Vikings were 40 feet below and head on to the ramparts, how on earth was that shot made?
Revealing mistake: Tony Curtis has his hand cut off in the film, and still his arm hasn't lost any of his blood or length.
Revealing mistake: When Kirk Douglas climbs the rope to the tower's window, you can see the flimsy rope. Supporting his weight, the rope should have been stretched tight. Right before he crashes through the window, you can make out the equipment supporting the stuntman. (01:40:20)
