Revealing mistake: When Mark is in the fitting room, it's obvious that his stunt double is playing one of the cuts in the 'mirror' as their moves do not match.
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.
Revealing mistake: The guys can't find the exam paper while snooping around the biology lab. So Tommy holds up a single key marked 'Home' suggesting they sneak into the teacher's apartment, like they know exactly where she lives, when they've never been there.
Revealing mistake: During the first round of auditions. The gal in the yellow shorts does fine. But then suddenly during the final ballet elimination, she can't keep up with the other girls and makes mistakes before Zach kicks her off.
Revealing mistake: When the Pillsbury alien comes in to the pool house, a bright white light turns on from the far left. It is supposed to be emanating from Pillsbury. The color is also incorrect.