Revealing mistake: This happens in the second ceremony when Wolf didn't press the button to shut off the lights to steal the golden dolphin because of the good comments. Few seconds later, the lights shut off, and you can see that the meteor on the top disappears at the time.
Revealing mistake: Obvious use of a "green screen" when Elvis and Dylan are sitting on the steps in the stairwell. The five distinct steps that could be seen behind them become a gray wall and the blue handrail posts to the right of the screen become oddly grouped, appearing to be parallel to the right side of Elvis' shoulder/back. (01:09:00 - 01:09:25)
Revealing mistake: In the scene wherein Detective Marquez and Senora Borden are drinking wine by the (indoor) pool, the back of Det. Marquez's head is disproportionately large. Front views of Det. Marquez often show his head tilted to the left, but rear views usually do not and his head might even be tilted to the right. Also, Senora Borden's eyes do not appear to be aimed correctly at Det. Marquez's (especially since they are facing each other with heads tilted to the right). Use of stand-in and/or green screen. (01:02:30 - 01:03:10)
Revealing mistake: The $100 bills in the briefcase looked quite fake and were obviously a prop. (00:13:40)
Revealing mistake: When Chris Evans is dragging the girl into the maze at the end you can see the burn mark on his shoulder creasing with his shirt.
Revealing mistake: The "snow" that Kip and his friends jumped into after leaving the bath house was obviously fake (like the "snow" on the pine trees). Beads of "snow" do not fly into the air when impacted by a weighted object, such as a body. (00:22:32)
Revealing mistake: When Otto, Tommy and Marisol find the frozen cat outside of the house it is a puppet prop. A few seconds later Tommy is holding it now back to a real animal and is bone dry.
Revealing mistake: After the shark got Lisa, Annie climbed atop her overturned kayak and was lying with her stomach about mid-way on the kayak with her feet over the back sides. The kayak was not long enough for Annie to have her body on half of it; her legs did not look real (odd-shaped and disproportionately short/CGI). When Nic got to the kayak, Annie's toes were on top of the (overturned) kayak instead of her feet hanging over the sides. (00:36:21)
Revealing mistake: In the underwater view of the fish, the ice hole is almost perfectly round and the ice appears to be quite thin - nowhere near the several inches Jason and Ben have to chip away to reach water. (00:33:55)
Revealing mistake: Corporal Shah is tied and on a chair in the command center. He then receives a powerful blow to his left check, knocking him sideways and rendering him unconscious. But his glasses do not even move a millimeter.
Revealing mistake: The French tanks that attack Paul et al. Towards the end of the second act are supposed to be Saint Chamond tanks. There is only one of those left in the world, and it is not on screen: the undercarriage and tracks don't even come close to looking like that of a Saint Chamond, because it's actually a BMP-1 dressed up to look like a Saint Chamond.
Revealing mistake: The size of the spider walking off Sam's face becomes disproportionately smaller too fast compared to its size while on her cheek plus the spider's awkward movements are indicative of CGI. (00:02:20)
Revealing mistake: The owl that JP saw was obviously "fake" (stuffed or CGI). Its nose was crooked and its puffy cheeks made it look like it had cheek filler injections; owls have flat faces. (00:32:50)
Revealing mistake: The cell bars appear to be about 4" apart, but are much wider to accommodate the width of The Artist's face/head when there's a close-up of him next to the bars. (01:13:50 - 01:15:09)
Revealing mistake: The front and rear views of the house did not seem to properly fit together. The rear view showed more sections, making the house longer than what the front indicated and had three high chimneys compared to only one from the front. The rear view also showed several trees that would be aligned in front of the house, but the trees did not appear to be situated that way. (00:27:49 - 00:29:52)
Revealing mistake: Younger Tom dropped his policeman's jacket onto the "fire" and when Younger Marion came over to the fire (almost 30 seconds later), the jacket still had not caught on fire. The next time the jacket was shown, most of it still looked unscathed by the fire. (01:33:30 - 01:35:36)
Revealing mistake: The guy with the sunglasses changes from behind and in front of shots. (00:09:46 - 00:10:15)
Revealing mistake: Becky calls Dan on her iPhone, as she puts it to her ear you can still see the contact info while Dan's voicemail is playing and not the actual call duration screen. (00:05:21)
Revealing mistake: The stairs are a prop. About a dozen steep steps - just to the landing - are almost as high as the front door. (00:55:48)
Revealing mistake: When William and Jack open the door, enter the room, and walk past the helium-filled balloons (tied to a chair about 4' away), the balloons remain immobile. Due to how light helium balloons are, just opening the door or breathing nearby would be enough to cause the balloons to move somewhat - if they were actually there. (00:16:00)