Deliberate mistake: When "Legs" lowers the Pez duck named Ducky down through the removed lightbulb hole, to ring the doorbell, the lightbulb housing is bigger than the hole but they bring it up through the hole to remove it. (01:03:55)
Deliberate mistake: Sid burns a hole into Woody's forehead in the middle of the film, but by the final scene (as the toys are waiting to hear what Andy has gotten for Christmas), the burn hole is completely gone. [Disney takes the attitude that violence is okay in their movies as long as the signs of it disappear by the end. Still a mistake but that's the reason.] (00:43:35)
Deliberate mistake: The license plate on the back of Andy's car says A-113, while the license plate in the front of Andy's car says A-111. A deliberate nod to room A-113 at California Institute of the Arts, often used by alumni, but a mistake regardless.