Deliberate mistake: Grug's loin cloth gets ripped by a lion at one point. The rip magically fixes itself just moments later. (00:53:15)
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: At the end during the car chase, the blue car goes under the lorry trailer. All tailors are fitted with safety side bars to stop this happening, they have been deliberately removed for the action scene.
Deliberate mistake: The whole premise of the movie is 'artistic license' so to speak; the protagonist signs himself up to the bone marrow donors register, called ADMO in his country (Italy). But he is still a minor, and that is strictly not allowed. Not even with a written consent of the parents as shown in the movie.
Deliberate mistake: In the scene where Mindy saves the dressed-up Dave from the street thugs and almost gets caught by the police. The female voice over the police radio remarks that the suspect is "under five feet" (below 152 cm). As she flees, she uncovered her motorcycle which appears to be a Ducati 1199 Panigale. The Panigale has a seat height of 82.5 cm, which means that by proportion, Mindy cannot sit on the bike with both feet flat on the ground (as a comparison, I'm 5'9 / 175 cm and still have to tiptoe a little bit on the Panigale, so even if she's slightly taller she still couldn't). Yet in the end scene where Mindy drops Dave at home after the final fight, she seems to be able to sustain the bike with both feet only slightly tiptoed, although her boots are not that tall. (00:13:20 - 01:34:30)