Deliberate mistake: Bowser has several teeth that appear and disappear throughout the movie. The best example of this is when Mario is trying to grab the Power Star. We see Bowser snarl at Mario before he picks him up. There is a gap between his two front teeth. However, when the scene cuts from Mario's horrified face to Bowser's face, there are now extra teeth inside that gap.
Deliberate mistake: When Flash is at the coffee store, the pavement is dry. When he exits the place dressed as The Flash, it's wet for cinematic purposes, but a mistake nonetheless.
Deliberate mistake: A car plummeting 10 metres off from a plane, landing on two cars as if they were a pair of soft gymnastics pit mats, just to keep on driving without a single scratch - let alone a mechanical breakdown or the blowing up of a tyre - defies all laws of physics and common sense.