Revealing mistake: Throughout almost the whole movie Harry's glasses don't have lenses in them. Only in two or so scenes do they appear.
Revealing mistake: When the 2nd BMW SUV is blown up on the dock, you can see the underside of the vehicle which reveals how they removed the drive shaft to help reduce the weight of it in order to flip it easier. There are also 2 jets of white gas seen coming from 2 pipes under the rear bumper which are what launched the vehicle end over end.
Revealing mistake: Towards the end of the movie, when Steve Austin is on fire during the fight, you can see it is a stunt man wearing a burn suit for a split second.
Revealing mistake: The overhead shot of Aron swimming at the end of the film shows him having two full arms.
Revealing mistake: When Cuchillo is about to be shot by Isabelle, you can see the bullet-hole-effect go off too early, due to bad editing. It's exactly in between that scene, when both actors are from the side, and as the scene changes to where Isabelle is seen from the front. (00:34:25)
Revealing mistake: During a large battle scene between the Fire Nation and the Northern Water Tribe, the camera pans to reveal a Fire Nation soldier fighting with no one.
Revealing mistake: When the main characters enter the underworld, there is a shot of them walking past a burning fountain. If you look closely at the shadows of the characters, they don't correspond with the lighting coming off the fountain.
Revealing mistake: In the beginning scene when the dragons are attacking Berk, it shows several sky torch things being raised into the air. As one closest to the camera is rising, a Viking throws a burning stick at it to ignite it. If you watch it closely, you can see the torch starts burning first to the far left, well out of reach of the thrown fire. Even allowing for fumes igniting, the fumes nearest the flame should light first.
Revealing mistake: Horvath is trapped in the bathroom mirror, and after knocking on the mirror from the inside, a boy comes over. You can see that the shadow from the boy's shoulder is falling on Horvath, and when he turns and falls over, if you watch closely, you can see that the boy bumps into Horvath's arm. This is because the boy actor is standing in front of Horvath's actor to achieve the mirror effect.
Revealing mistake: Eustace, in dragon form, is flapping his wings with all his might as he tows the ship. But in the overhead shot, while he continues flapping, his shadow on the water below is completely motionless.
Revealing mistake: In a close-up, just after the defeat of the Jabberwocky, the White Queen collects the Jabberwocky's blood dripping from its teeth into a vial. Cut to a wider shot with the vial just over half full, you can see that the drips are still being caught by the vial (ie, they don't drop past it onto the ground), but the level of blood in the vial doesn't rise, revealing that it is done in post-production.
Revealing mistake: When Dominic West is captured and chained in the Pict village, you can see a hearing device in his ear. (00:38:55 - 00:41:35)
Revealing mistake: On Gulliver's MacBook when he is plagiarizing , he has the wrong program active at the top (Finder for Macists), when he is typing on the keyboard. He also doesn't have a single word-processing application open, which can be viewed at the bottom.
Revealing mistake: The can of "Chernobly" is supposed to be from Moscow, and the lettering on the can contains at least one Cyrillic letter. However, the name printed on the can is nonsensical, using random Latin and Cyrillic letters in an effort to look Russian, but the letters don't spell a word and means nothing in Russian.
Revealing mistake: When Jensen is investigating the missing 4 million dollars from the account, we see the screen on his laptop. Among other things, it shows a picture of Fadhil's passport, which looks like it has a watermark on it, readable as http://slawek.com. Indeed, going to http://www.worldpassports.org/americas/pages/bolivia.htm you will find the passport pictured there. (01:01:35)