Other mistake: When one of the agents is ambushed by the Tooth Fairies he is reduced to a skeleton, with his teeth still visible. However, it was earlier stated that Tooth Fairies start by eating the teeth, then finish off the rest of a body.
Factual error: A toy modern four-door automobile and a clear plastic ball can be seen as the children play when the Burgermeister comes in on his wheelchair. Both unlikely for a story set (presumably) in the 1800's, at the latest.
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.
Visible crew/equipment: When the doctor wants to study Electro, a green screen and some other things are reflected in his glasses. (01:14:10)
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: 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: 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)
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: 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?
Factual error: Finishing his rounds on the morning of Christmas Day, flying over downtown Chicago, the sun is over the horizon west of Chicago, Sunrises occur in the east, not the west. (00:26:10)
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?
Revealing mistake: When Qui-Gon, Jar-Jar, and Padme are eating at Anakin's house, Anakin's mum pours water for Qui-Gon. But when she gets to Jar-Jar, she tips the pitcher but no water comes out. (00:39:10)
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)
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)
Factual error: Jonathan is lying in the middle of the skating rink when the second cashmere glove falls upon him. Looking around, he notices Sarah at the edge of the rink. Despite Sarah being a female and the fact that it is snowing, even Nolan Ryan would have a difficult time throwing something as light as cashmere that distance. (01:22:05)
Continuity mistake: When the Mystery Men smash their "Magnetic" Herkimer bus through Casanova's Castle's main gate you can see a number of the lights mounted to the front of the bus are smashed, however, in the next couple of front on shots, you can see that all lights are working and intact.
Factual error: When Reese Witherspoon's character is sitting at the desk reading, there is a cheerleading trophy and the cheerleader on it is wearing a mini skirt, - they didn't have mini skirts on the cheerleading outfits then. (01:08:20)