Other mistake: When the switch is thrown to electrocute Terrence and Phillip, it's pulled downwards. A few shots later, we see Cartman jump in to save T and P by turning the switch off. He also pulls the switch downwards instead of pushing it upwards. (01:06:05)
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 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)
Factual error: In the opening short "Pikachu's Rescue Adventure" in the Bellossom song and dance scene a Poliwhirl calls itself a Poliwrath. This is obviously a mistake because of the body differences between the Pokemon.
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