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].
Continuity mistake: When Sam and the other girl fall down the mountain, at one shot Sam unlocks the girls snowboard and it drops down the mountain but at one shot before the ski patrol throws the rope down to them you can see (for a second) on the right side of the girl, the corner of the snow board. Then she doesn't have it.
Continuity mistake: When the Iron Giant follows Hogarth home they cross a railwayline and the Giant starts to eat the steel rail. During this scene you can see the distance of the railway sleepers changing from a fair distance apart to close together over the course of the shots. In the same scene you can also see that, although there is a crossing with lights, no vehicle could possibly pass as the rail has no crossover facility at that level. (00:24:30)
Continuity mistake: When singing the song about what they would do if the monster came to their room in the night, Simon puts on Alvin's duvet/blanket as a cape. It then shows an imagination sequence where the blanket is a correctly sized cape to fit him. When it returns to the real world, the 'cape' is the size of his imaginary cape, nowhere near the size of the bed.Dan Moat
Continuity mistake: After the party, a girl with a maroon shirt and grey skirt runs out of the house twice.