Revealing mistake: Just before Michael and Ellie get out of his car, a fire extinguisher is seen mounted above the dash. Michael opens the hood and the engine begins smoking. Michael reaches into the car for the extinguisher. You can see through the windshield that he is handed another extinguisher instead of removing the one from its mounted spot. The mounted extinguisher is still visible in its holder. Likely done to preserve pacing so he doesn't have to fumble with the clamps on the mounted one.
Continuity mistake: When Mickey is being interviewed for the yearbook, watch out for students that walk in his opposite direction. There are obvious recycled extras appearing in multiple shots coming from the same direction, such as the blonde with checkered top paired up with a guy in a blue shirt. (00:09:00)