Continuity mistake: When Buzz and Woody are riding RC, holding onto Slink in the end, there's a shot where the truck turns to the left on a bend. Slinky gets stretched further, and RC goes off to the right side of the road due to centrifugal force. We can see that RC is going to go under a parked car. The camera switches to the front and we see the car pass from further right. They never end up going under it and tangling Slinky in the wheel. (01:12:00)
Other mistake: After throwing Woody to the floor, Sid raises the window shade and tries to burn a hole in Woody's head by using a magnifying glass to focus the sunlight. Sid is leaning over Woody with his back toward the window and yet he does not cast a shadow on Woody. In addition, the position of Sid's body would block the sun's rays from hitting the magnifying glass but the close-up shows the narrow beam of light hitting Woody's head.
Continuity mistake: Towards the end when Potato Head and Ham are playing Battleship and Woody is yelling from Sid's room, Buzz is wearing the apron that Hannah put on him. He's wearing it throughout that whole scene except when the toys in Sid's room are fixing him and Woody says; "you're not gonna eat him, you monsters."
Continuity mistake: When Woody plans to knock Buzz behind a desk, if you look closely at the globe in a box next to the bulletin board, it is slightly off-position in its stand. Later, when the bulletin board begins to fall on the globe, the globe is positioned correctly. (00:24:40 - 00:26:00)
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.