Continuity mistake: When the law enforcement officer arrives, there is a tight close up on the handle of his .38 revolver. When one of the aliens scans his body, an image of a .45 1911 appears instead.
Other mistake: Towards the end of the movie, when Superman drops Gus off at the coal mine, Gus begins talking with the coal miners about him and Superman. He then rips open his shirt (as if he had a Superman costume on underneath). How did Gus know that Clark Kent tore his shirt like that in order to change into Superman, or keeps his suit under his clothes at all? The only people who know this fact are the ones who have seen the transformation from Clark to Superman, i.e. the audience.
Other mistake: When Nebbercracker is on the stretcher and is being wheeled away, the grass pulls off one of the last wheels. When the stretcher is loaded into the ambulance both of the back wheels are intact.
Factual error: Near the beginning of the film before James McAvoy heads up to the house for the evening meal, he is seen looking up through a skylight when a Lancaster bomber slowly flies overhead. At the time it was was supposed to be 1935. The Lancaster bomber did not fly until the beginning of 1941. Can't be an Avro Manchester either, they only had two engines and first flew in 1939.
Visible crew/equipment: Throughout the movie, in the shots of the guys on the alien planet, the white reflector screens and film crew's reflections are visible in their sunglasses. (00:40:20)
Revealing mistake: In the library scene when Richie sees Pennywise the clown, all the balloons filled with blood are popping on people who aren't supposed to be able to see them, but one lands on a lady and you can see her jump as the balloon pops.
Continuity mistake: Darth Maul's neck is black, but when he is talking to Darth Sidious on Coruscant, his neck is flesh-toned. (00:38:45)
Continuity mistake: In the dormitory, when lovestruck Ron is going gaga over Romilda, he is wearing a brown sleeveless tee shirt and its tan trim has many holes. When Harry brings Ron to Slughorn, Ron is still wearing that tee shirt, but now some of the holes are gone and the rest of the holes have changed position. (01:26:50)
Revealing mistake: Mr Hyde makes no bubbles when growling underwater. (01:11:30)
Plot hole: During the scene where Merida gives her speech on "breaking tradition", her mother, as a bear, moves silently behind the majority of the crowd, so they don't see her. Fair enough. However, Merida and her father's clan are all looking in the same general direction (towards the crowd) while she's speaking - how does no one from Merida's clan see a bear moving at the back of the room?
Visible crew/equipment: Michael J. Fox is dancing on top of a bus as the Teen Wolf. The camera swings just a little too far toward the back of the bus and a police car that is escorting the camera car and bus is seen in the rear with its red lights going.
Continuity mistake: A blond boy in a light brown shirt is attacked by a crow and goes from having no blood on his neck to having a lot of blood smeared on his neck between shots. (01:14:10)
Continuity mistake: When the evil king's female assistant is "turned into" Odette, and Prince Derek is dancing with her near the end, he puts the locket on her. The chain goes around her hair, and in the next shot, it's under her hair. They were dancing the whole time, so how could she or Derek have pulled her hair out of the chain?
Continuity mistake: Once the chipmunks are inside the food cupboards, they begin to devour everything inside. Theodore is seen chewing off a corner of a box of Lucky Charms cereal and eating the cereal that pours from the hole. But a few shots later when the same box of cereal can be seen, the hole that Theodore gnawed from the corner of the box is gone and the corner is fully intact. (00:11:00)
Revealing mistake: When Brom (disguised as the horseman) throws the jack-o-lantern at Ichabod, there is a shot from Ichabod's perspective showing the jack-o-lantern flying toward him. It jiggles from side to side, revealing it was travelling on a wire.
Plot hole: So he needed the help of a big strong burly guy to flip the safe with the body, end over end to the pit, but he somehow was able to easily get it out of his basement and into the back of his car by himself?
Continuity mistake: In the scene where Jonathan picks up the scarab, it breaks open and the beetle inside starts to crawl under his skin. We see Brendan Fraser tear Jonathan's shirt and cut the beetle out of him. However, in the very next scene, we see Jonathan walking into the temple, his shirt is intact and there is no blood to be seen. (01:37:05 - 01:38:30)
Plot hole: When Alex and Clear are sitting and having coffee they are on a corner. He looks in the window to see the bus pass, and as he looks to see if it is there, it's not. As the camera pans across the street, there is some construction going on which is blocking that whole road from being used, but then Terry, Carter's girlfriend gets "waxed" by the bus - no way it could have got through all that construction.
Visible crew/equipment: When Ashley is running down the corridors before escaping back into her medical room, you can see the dolly that The Engineer chasing her is being pushed on. (01:04:50)
Plot hole: When Astrid gets on Toothless for the first time, Toothless takes off uncontrollably and tries to scare her. Hiccup seems to have no control over him at this time. How is that so if with the new tail fin, Toothless cannot fly without Hiccup's precise control of the tail fin? That whole sequence would have fallen apart. This mistake was even admitted to on the DVD commentary. (00:53:35)