Revealing mistake: After Spirit gets his second wind when the Colonel is attempting to break him, he breaks the girth/cinch strap by catching it on the fence. At one brief point, the pole of the fence actually appears to pass between Spirit and the girth of the saddle.
Revealing mistake: When Arnold asks Bridget how much the equipment costs, as she says, "It's on the house," her eyebrows disappear for one frame. (00:36:35)