Revealing mistake: An enraged Cheetah almost literally mops the White House floor with Diana flailing her around with the lasso. Wonder Woman is sent back first into a pillar, which disintegrates from the impact. Very good, but not so good is the other piece of pillar that comes down and bounces like rubber by her. (01:51:45)
Revealing mistake: During the dance number in the airport, Santa grabs a security guard who then starts break dancing. It's obvious this dancer is a stunt double as he's younger and skinnier than the real guard.
Revealing mistake: The nefarious villain has just revealed to Prince Charming that he has kidnapped the princess, and shows her to the crowd as a big burly smurfy monster is holding her. The crowd in unison gasps and looks horrified...except an extra who just can't keep a straight face. (00:07:35)
Revealing mistake: In one of the scenes in the ballroom you can see that the thumb claw of the head witch is put on top of her real thumb.
Revealing mistake: When Maya Rudolph and Tim Meadows are in their car at the drive-in theatre, whilst Maya Rudolph says "We got Hubie Dubois spying on everybody", there is a close-up shot of the wing mirror with Hubie's car reflected in it, along with several other cars and a building in the background also reflected. Despite being a reflection, any text or numbers reflected in the mirror are not reversed. The number plate on Hubie's car is spelled out forwards, and the sign "Salem Drive In" on the building in the background is spelled forwards also, and not reversed as they normally would be in a reflection. (00:49:17)
Revealing mistake: In the opening pre-calculus class, Mara bending over to the side of her desk is what enabled her to avoid being splattered when Kaitlyn - sitting in front of her - "exploded." It was also a cue that the "blobs of blood" were about to be strewn across the classroom. The boy seated at the last desk behind Mara moved his right hand up to his forehead (similar to how one would block sunlight) in anticipation of getting splashed with blood. After some of the "blood" landed on him, he quickly moved his hand away from his face. (00:00:35)
Revealing mistake: Although it appears that Edgar (and later Norman) put his eye up to the hole in the wall to look into the opposite room, the eye is obviously fake. Too much of the sclera (white part of the eye) is showing and the upper eyelid is too far above it; the upper eyelid typically reaches or partially covers the top of the iris (colored part of the eye). Also, the eyelashes go downward instead of being curved upward. (00:18:05 - 00:19:49)