Deliberate mistake: At the start of the film when the commentators are explaining the tie situation between the 3 cars the green arrow to the car is out of alignment and misses the car, instead pointing at the track. Pixar Creative Director, Jay Ward, who is this film's team manager (as well as art coordinator) has stated that this was deliberately done as a joke, for fun. It's a little bit off, in the same way that Chick Hicks is a little bit off. This is the video with Jay Ward explaining: https://youtu.be/ZkJre-eC-zE?t=25.
Continuity mistake: In the scene when Jack Black is about to be unmasked and the kids are watching his match on TV, Chancho goes to to cover the TV. He is wearing a pink shirt but in the shot of him covering the TV he is wearing a white singlet.
Continuity mistake: In the scene where Haley is sitting in the bathtub full of ice, she is wearing a black sports bra. The shot then switches to some of the girls watching a news report from the Worlds competition. It then switches back to Haley, who is now wearing a gray sports bra.