Deliberate "mistake": When Boo laughs repeatedly while playing hide-n-seek with Sully in the men's room, nothing happens to the electricity - no surges as with all other times she laughs. [In the audio commentary by the directors, they explained that it would've been distracting if an energy surge occurred every time Boo laughed, so they simply didn't address the issue. A reasonable course of action, but still a mistake.]

Continuity: After the Scare Floor shuts down at 6:00 and Sulley goes back to do Mike's paperwork, the clock reads 5:48. After he returns again to put Boo back, it clearly shows 5:48. Finally, after Randall leaves and Sulley leaves the Scare Floor for the restaurant, the clock reads 6:48.

Continuity: When Mike is bringing Sully to the fixed door he has no slivers or band-aids on his hands, then when he says "it was a lot of wood to go through" you see he does.

Other: In the scene when Mike, Sully, and Boo were all hiding from Randall in the bathroom, all three of them are standing on the toilet in the same stall. They look straight ahead and see Randall using the sink in front of a mirror. But, a minute later Randall is busting open the door to each stall. When he hits their stall door open, he is looking the other way, and doesn't see them. Yet he would have seen their reflection in the mirror. I realize that Randall's eyes were not looking straight ahead into the mirror. But, where he was looking, he would have easily seen a huge, bright blue and green monster.

Continuity: In the opening scene, on the floor there is a toy train on circular tracks when the monster sneaks in. When the monster trips backwards over the ball and skateboard then falls onto the jacks, the train and tracks are gone.

Other: Near the end of the film, when the identity of 0001 of the CDA is revealed, number 0112 is shown both standing next to 0001 as she enters the room and behind Sully and Mike on the opposite side of the room.

Other: When Sulley and Mike take Boo into the Factory, they see all of the CDA agents. There are 3 talking to Mr. Waternoose(as we see seconds later). One of them is number 00002. When they are done, they escort Mr. Waternoose to somewhere else. However at that very second another agent comes in with a metal detector thing. His number is 00002.