Deliberate mistake: In the Spanish version, the headlines of the newspapers are in Spanish, but the rest of the articles are in English. It helps supports the narration, but it causes a very weird effect.
Deliberate mistake: When Jafar sees Aladdin reflected in Jasmine's crown, Aladdin is the only thing visible. This isn't possible- we should have also seen the background of the room, the objects around him, etc.
Deliberate mistake: In Monsters, Inc., when Mike and Sulley walked through Monstropolis to go to the company, Mike said to Sulley "You've been jealous of my good looks since the fourth grade". In this film, we're told Mike and Sulley met in college. [In the commentary, director Dan Scanlon explained that there was a lengthy scene that would have followed Mike and Sully throughout their years in elementary school, but it would have slowed the pace of the film and would have reduced the impact of their rivalry. Rather than spend a lot of time on a back story, Scanlon decided to have Mike and Sully meet in college, even though this was inaccurate.]
Deliberate mistake: The little red-haired girl boards a bus with other children who are headed to summer camp. As the bus drives away, there is nobody in the driver's seat. This movie maintains Charles Schulz's policy of never showing adults in his comic strips or animated television specials, but a bus driver could at least have been depicted in silhouette.
Deliberate mistake: When Bender wins the poker tournament with five kings, Leo Wong holds up five fingers (on one hand). But all the characters in Futurama only have four fingers on each hand. (Confirmed on DVD commentary).
Deliberate mistake: There was no possible way for Edith to still be alive after the spiked coffin closed in on her. There are spikes on the doors and at the very back and sides of it, and she couldn't have squeezed in to brace herself. Probably done for obvious reasons, but still a mistake nonetheless.
Deliberate mistake: During the first aerial angle of the pirate ship they are heard singing, but the ship is empty. Most surely due to the complexity of drawing detailed tiny pirates.
Deliberate mistake: Jimbo gets shot in the front with three plastic arrows on his chest when protecting Boss Baby, but they just suddenly vanish. A scene later, Tim shoots him completely in the back, but Jimbo is covered in arrows from the front and back. There was nowhere near enough time for him to turn around, and Tim had already stopped firing to grab the cassette tape.
Deliberate mistake: When the grandfather clock chimes at 12:00, look at it when the clock ticks. It starts at 11:58 but then ticks to 12:00. The clock has somehow ticked 2 minutes instead of 1 minute.
Deliberate mistake: At the speed trap, Tom points his radar gun at a turtle. From his perspective, he seems to be looking through some sort of scope with cross hairs and numbers on it at the turtle to line up the beam. However, when he then looks at the radar gun at the speed indicated as 1 MP/H, there is nothing on the gun where he could have been looking through such a scope. At best, the top of the run appears to have plastic iron sites. The scoped view would not have been from the device itself perspective since it would not need cross hairs or numbers on said cross hairs as that would be for a person looking through it to have reference points. This scope view of the turtle was most likely just added by the film makers to have a better visual representation of Tom aiming the radar gun at the turtle. (00:04:29)
Deliberate mistake: When Julien is about to pull the switch to turn the power off in the Monte Carlo casino, the sign above the switch says "LE POWER." Monte Carlo is in Monaco, where the language is French, so the sign should be in French. Obviously "THE" is in French as "LE." But "POWER" is not in French. The sign should have said "LE POUVOIR." (00:10:15)
Deliberate mistake: When Metro Man flies towards the observatory to save Roxanne, we see a typical "the-characters-see-what-the-audience-sees" shot - a Super-Man-esque shot of him with his arms stretched out in front of him with his fists clenched. This shot is then projected onto a monitor that Minion is watching. It would be impossible to achieve this. It's as if there's some sort of camera on top of the observatory filming Metro Man, which there isn't. We see the observatory enough times to see that there isn't, and even if there was, the angle at which it would need to be at would be impossible to achieve. The shot of Metro Man on the monitor is positioned right in front of him, panning backwards. A camera would need to be very long to achieve this kind of shot, but there simply isn't one present.
Deliberate mistake: I know this has been disregarded for the fun effect, but gasoline motors require air to work. When Edgar drives his tricycle into the river while being chased by Napoleon and Lafayette, it should have stalled and stopped working.
Deliberate mistake: When Lex busts Joker out of Arkham Asylum, he uses his Deconstructor gun on the LEGO wall. It takes it about 8 seconds to pull the LEGO apart for Joker to get out. The same amount of time is taken when he demonstrates it to Joker and frees Penguin. Yet when Joker grabs it and uses it to free Catwoman and Two-Face, that time is cut in half. And then yet again when they are leaving on the chopper, Joker fires it 3 more times, freeing Poison Ivy, Harley Quin, and The Riddler. It barely takes a single second on each of those. (00:17:40 - 00:19:35)
Deliberate mistake: Throughout the movie we hear every animal (and insects/arachnids as is the case with Charlotte and her offspring) with one exception. Every time Charlotte catches her meals in her web we never hear the fly or other insect she is descending upon cry for help, or plead with her to be spared. This is deliberate due to this being a kid's film but still bears noticing as a mistake due to the fact that they are the only ones rendered mute for plot convenience.
Deliberate mistake: When Big Gay Al sings his song, he sits at the edge of the stage. In a wideshot the soldiers are just watching, yet in a closeup they're all waving lighters. (00:59:25)
Deliberate mistake: In multiple shots, Stitch's ear notches move higher in places or vanish completely.
Deliberate mistake: In the Swedish dub, they euphemistically replace the words "execution" with "punishment."
Deliberate mistake: In the fire scene, Jon tries to catch Garfield from the chandelier at the main staircase. When Jon reaches out to grab Garfield, there is no rail on the stairs. It comes back in the very next shot & disappears again after Garfield says "Need a lift?"
Deliberate mistake: When Batman enters the replica of The Joker's apartment there's no place for The Joker to hide. Yet seconds after Batman enters, The Joker comes out of nowhere to hit him with a pot.