Continuity mistake: 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. (00:01:49)
Continuity mistake: At the beginning when you see the monster in the testing room from under the bed with the glowing eyes, you also see the soccer ball on the left side of the screen. This shot takes place on the side of the bed. After the monster gets scared, he backs up kicks the soccer ball, but it is now at the foot of the bed in the middle of the room. (00:02:35)
Continuity mistake: At the beginning when the monsters are at the testing room, you can see the boy in the bed seeing something opening the cabinet. He closes his eyes and opens them up again to see a sweater sticking out. But when another monster sees what he does wrong on the tape, the sweater isn't sticking out anymore. (00:03:40)
Continuity mistake: At the beginning of the film, we see Sully asleep in his bed and the alarm clock/radio on a bedside cabinet to the right. Later, when Boo climbs into Sully's bed, the clock/radio isn't there anymore. (00:04:50 - 00:32:30)
Continuity mistake: There is a purple chair and a green chair in Mike and Sulley's apartment. The green chair disappears when they are at the apartment with Boo later. (00:05:45 - 00:27:50)
Suggested correction: Didn't they use the chairs fabric to make Boo's disguise? The chair would have been ruined.
They only used Sulley's chair to make a costume for Boo. Mike has his own chair but we are never shown as to where he keeps the chair. He may have put the chair somewhere else in the apartment so Boo wouldn't her germs all over it.
Audio problem: When Mike and Sulley walk through Monstropolis, Mike goes to his car. An automatic unlocking sound from the car, but the keys Mike is shown holding appear to be the keys one would use to manually unlock the door. (00:07:20)
Suggested correction: Monstropolis is shown to have many things that operate differently from the real world. It isn't such a stretch to consider that car keys work differently as well.
Continuity mistake: Before going to the Scare Floor, Mike goes to get his paperwork from Roz. The paperwork first faces 5 o'clock direction. A few shots later, the papers suddenly face a 12 o'clock direction. (00:11:25)
Audio problem: Jerry counts down from seven. When he has to say one his mouth opens, but he doesn't actually say one. (00:14:38)
Suggested correction: Many times when counting down, three-two-one is silent.
Especially when filming something like this, so the numbers aren't accidentally recorded.
Continuity mistake: At the start of the workday, Randall opens the first door with the knob on the left and hinges on the right. When he comes back out, the knob is on the right and the hinges are on the left. (00:14:45)
Audio problem: When we see Mike during the slumber party, we hear seven bells ring for the seven filled cylinders, but there are only six cylinder-filling noises. (00:16:50)
Continuity mistake: When George comes out of the door with the kid's sock stuck to him the sock's toe points inward toward the middle of his back. When the CDA rushes in to remove it the sock toe faces outward. (00:17:40 - 00:18:25)
Continuity mistake: 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. (00:22:06)
Continuity mistake: When Sulley places the menu on the table he puts it face down (logo first), then when he lifts up the table, to quickly get Boo, the menu is face up. (00:26:05)
Continuity mistake: In the apartment, Sulley leaves a trail of Kreature Krisp for Boo to follow. The first one he places is white, which becomes green in the next shot. It's obviously the same one in both shots because of its position in the doorway. (00:31:00)
Continuity mistake: Boo shows a drawing of Randall. First, it's held in a portrait position, then in the reverse angle, it is now held in a landscape position. Then back to portrait position in the next shot. (00:31:30)
Continuity mistake: When a green monster named Frank was walking out of Monsters, Inc. on the second day, take a look at what's behind the door - It only shows passages to scare floors, but when Mike and Sulley (holding Boo in costume) walk in, the CDA is all over the place. (00:35:05)
Other mistake: In the scene where Mike and Sully walk in on the CDA overrunning the power company, there is a CDA agent with number 00112 behind the main desk, and another with the same number talking to the boss a second later. (00:35:10)
Other mistake: 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 also 00002. (00:35:20 - 00:36:10)
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.] (00:37:30)
Continuity mistake: When Mike, Sulley and Boo are walking to the Scare Floor after leaving the locker room, Mike's feet and legs are soaking wet. His feet are suddenly dry by the time they reach the Scare Floor. (00:38:45)
Suggested correction: Sully may have unplugged the alarm clock and put it somewhere else, especially when there's a "dangerous" child in his home, and he wouldn't want his things to get contaminated.
This correction is a stretch. If he doesn't want his things contaminated, why not remove the pictures and lamps? Why let her sleep in his bed with his blankets?
Bishop73