Revealing mistake: When Woody falls out of the closet wrapped in the string lights he hears Buzz's voice, and in the next shot as Woody sneaks up to Hannah's room we see Sid's open door and doorway, which looks perfectly normal. However, after Woody rescues Buzz from Hannah's tea party they both stop in the hallway, and there's another shot of Sid's open door and doorway, only this time it's not normal to say the least. Five of the six hasps, bolts, and locks that should be (and normally are) screwed into and attached to the inside of Sid's door (one hasp mechanism, third one down from the top, is attached to the door's frame) are now actually kind of floating there in mid-air right beside the doorway, as if there's an invisible door there. Weird that Pixar artists deliberately did this, but it's bizarrely funny to see.
Continuity mistake: After Dory reads the wall map while she's in the glass carafe, when Hank hides behind the rolling cabinet there's a long shot of the corridor with him at the far wall, then in the next shot from behind Hank a drinking fountain has suddenly appeared on the wall to the left, between two pictures.
Continuity mistake: When Mr. Incredible lands on the island, he gets stuck in his capsule, eventually smashing it to get out. He starts stretching, bending backwards. The angle lowers to show that Mr. Incredible's suit is now a two-piece, revealing his fat stomach. During the rest of the movie, the suit is a one-piece, so this wouldn't be possible. (00:35:15)
Continuity mistake: After Chuckles tells the story of Lotso we see the gang locked up at the daycare center. Jessie comforts Bullseye and looks at the word "Andy" on her boot (with the "A" on the inner side) . Woody returns and when the bell rings for the kids to go outside, we see Jessie on the floor. Notice that the "Andy" on her boot is now different (the "A" is on the outer part of her boot). (00:52:50 - 00:57:10)
Continuity mistake: When the dentist wants to put Nemo in a bag, it's a resealable one with a seam at the top. When he finally catches him, it has changed to a normal plastic bag.
Continuity mistake: Near the end of the movie when the 'false' Buzz Light Year is running along the air conditioning ducts his 'New Utility Belt' disappears then reappears again. (01:01:55)
Continuity mistake: Remy is reunited with his father in Paris. They are in a conversation at a little table. Remy's 'cup' moves closer to the edge of the table, towards our left, in several shots.
Other mistake: In the scaring simulation room, the alphabet wallpaper border at the top of the wall has the "J" written backwards.
Suggested correction: The walls of the room also have nonsensical drawings like a giraffe with two heads. The implication is that the monsters designing the room didn't entirely know what kids would actually have in rooms (like they didn't know that giraffes don't actually have two heads). So they thought that humans have the J backwards.
Whether or not the backwards J was intentional or as a joke, it would still seem unreasonable for the monsters to get it wrong when you see they got the pictures for each letter seen correct "jaguar", "kangaroo "pig", "quail", "rhino." I would at the very least call it a character mistake.
As the original correction said, it's just an example of the monsters not understanding the human world. Not a mistake.
Yet they know the alphabet? I doubt it.
Continuity mistake: On Riley's first day of school, she has a blue notebook on top of some other books on her desk. After her story about Minnesota, she sits down, where the notebook is now under another book.
Continuity mistake: When Wall-E presents Eve with the plant, he is facing her directly. When Eve is later viewing the footage from her security camera, Wall-E is shown facing at an angle towards the left of the screen, instead of straight ahead.
Other mistake: The monitor from inside Mack's trailer displays his whole face while talking to McQueen. There is no camera outside of Mack that can display him in that fashion.
Suggested correction: The camera in the trailer may be a TV video instead of a camera.
No, McQueen is talking live with Mack through this monitor.
Continuity mistake: After the old lady thanks Dash for saving her from getting crushed by the flung blue vehicle, that vehicle suddenly has been moved slightly to the left from its original landing spot. Also, another wrecked light blue vehicle was visible as the aforementioned blue vehicle hit the ground, after the old lady thanks Dash, it has suddenly been replaced by a white wrecked vehicle instead. (00:05:45)
Continuity mistake: When Mr Fredrickson opens the door there are 4 locks on the front door looking from the outside in. Next scene and consequent scenes there are only 3. (00:12:35)