Deliberate mistake: When Tarzan fights with the leopard, it scratches his chest. However after they fall into the pit and Tarzan comes out carrying the dead leopard, the scratches on his chest have amazingly healed. [It is a long-standing Disney tradition that no evidence of violence is shown on screen. Still a mistake, but there's why].
Deliberate mistake: Even though Hamm is flicking through the channels at the same speed, the side with Al's advert on it is visible for longer.
Deliberate mistake: When Big Gay Al sings his song, he sits at the edge of the stage. In a wideshot the soldiers are just watching, yet in a closeup they're all waving lighters. (00:59:25)