Deliberate mistake: When Eddie and "Jennifer" are walking around the house alone, she is trying to tell Eddie that she's really Sara. But by the time she is explaining that, Eddie has disappeared. She doesn't find him until later. But from the moment she finds him (and he is talking to her) he calls her Sara, despite never actually hearing her say that. Also, after they all get back together, a few of the other people start calling her Sara as well, but no one actually heard that either.
Deliberate mistake: When Norman picks up Marion's supposedly naked body to carry it to his trunk, a bra is visible through the shower curtain. Gus Van Sant included this goof in his 1998 remake.
Deliberate mistake: At the end of the movie when everyone is on the bridge, the one female cop roundhouses the bad guy, who is clearly a white male in his 50's, but his stunt double is an Asian man (with different colored hair). They use the same stunt man a few other times for people he doesn't even look like.
Deliberate mistake: In the scene in which Ace is in the asylum, he breaks into a storage closet to view Finkle's belongings that were left behind when he escaped. At first the doorframe is such that the door closes against about an inch of wood, meaning the lock would be behind this wood, so Ace couldn't pry it open. In the closeup, the door's flush against the frame so Ace can use the sign to get between the door and the frame. In the wide shot it's back to how it was. (00:58:55)
Deliberate mistake: Bare shoulders are forbidden in the Vatican premises, so the sexy dresses in the party would not be allowed.
Deliberate mistake: Almost trivia, but not quite. When Mystique's looking through the guard files to find a suitable candidate, lots of photos flash up very quickly before she finds the guy she uses. Of note is that Bryan Singer pops up in guard uniform (with his own name), and so does someone called "Donner, L". This is most likely referring to Lauren Shuler Donner, one of the producers, and sex is specified as "F", but the photo is of a stubble-coated man. (00:23:10)
Deliberate mistake: The rail line was supposedly not used in 30 to 40 years, however, in the exterior scenes approaching the bridge where the mile markers were, the tracks are well maintained, has no vegetation, and the rails are shiny, indicating a lot of train use.
Deliberate mistake: After Ash's body is incinerated, the interior walls of the Nostromo appear more metallic and grey than they were before. According to Ridley Scott, this was done deliberately to make the alien's presence appear more menacing.
Deliberate mistake: When Peter and Miraz are fighting, Peter stabs Miraz and then brings the sword back up for the killing stroke. There is no blood on the sword. This is deliberate on the part of Disney, so as not to show blood, but a mistake nonetheless.
Deliberate mistake: Bosley is a school crossing guard trying to help the Angels. The children behind them say they are gonna be late for school. Of course they're going to be late because there is not a school within 10 miles of where they are standing. There's trees and what looks like a huge mountainside on the other side of the street. You can see this more visibly as the car that is about to run over Bosley is approaching. Done for a gag, but still ridiculous. (01:09:05)
Deliberate mistake: Has there ever been a more obvious body double than the one used for Angie Dickinson in the shower scene? Not only does the top of every shot stop right at the collarbones, she is much taller than Dickinson, she has a much deeper tan and (of course) her breasts are much, much bigger. In fact that is Victoria Johnson, Penthouse Pet of the Month for August, 1976.
Deliberate mistake: When the two assassins enter Leo's bedroom and try to gun him down, the one on the right has left his tan overcoat open. He's the one that escapes from Leo initially. Shortly thereafter, Leo guns him down, firing up into a second story window. At this point we see that the assassin's coat is now buttoned up, probably to conceal the numerous squibs used in his death scene. (00:41:00)
Deliberate mistake: In the chase through the tube station, Bond and Silva both slide down between the escalators. On the London Underground, this area has hard vertical signs at regular intervals, precisely to prevent people sliding down. (01:31:50)
Deliberate mistake: When the Creeper gets stabbed through the eye with the javelin, it goes through the front of his eye, but when it comes out the other end the eye is facing backward. (00:50:00)
Deliberate mistake: After the trilithium missile hits the sun, it is shown going out in real time from Veridian III. As the planet is relatively earth-like, it is several light-minutes away from the sun. The filmmakers wanted it to be obvious that the missile was successful, so they ignored the speed of light. (01:20:35)
Deliberate mistake: In Paris' death scene, he blows alcohol onto his torch that illuminates the creatures around him. However the area is still illuminated after the light from his torch has disappeared. (01:12:05)
Deliberate mistake: There are a number of things wrong with the roller coaster scene (besides the obvious impossibility of a crash like this actually occurring): 1) The restraints use ratchets to lock, not hydraulics. A coaster of this type wouldn't even have any hydraulic lines. 2) The attendants didn't check all the restraints. This is ALWAYS necessary, on ANY ride. 3) On any roller coaster, the Dispatch button (or "Start" in the movie) must be held down until the train is clear of the station. This is a safety feature to make sure the attendants are clear of the moving train. If the button is released before the train is clear of the station, it will stop. 4) At the bottom of the lift, the lift chain curves to follow the track into the station. This is impossible, a lift chain cannot curve horizontally, only vertically (normally at the top of the hill).
Deliberate mistake: If you pay extremely close attention to the scene of all of the Decepticons responding to the small Transformer's message regarding the location of the Allspark, notice that the shot of the police car and the fake helicopter pilot are duplicate shots used earlier in the film.
Deliberate mistake: When Agent Hoffman writes the letter to Amanda, he puts the envelope so her name is pointing down, yet when Amanda opened this drawer in Saw III her name was at the top. The director had to do this or it would have revealed Hoffman was the new apprentice all along.
Deliberate mistake: When the New York subway is flooded the interior shot shows the station is Wilshire Blvd. Wilshire Blvd is in Los Angeles and the film clip appears to be stock footage from the Universal Studios Tour ride.