Revealing mistake: When Austin enters the bathroom at the casino, keep your eyes on the door during the scene - it opens by itself before closing. (00:31:10)
Revealing mistake: In one shot when the boat is pulling away from the waterfall, you can clearly see that the shot is the same one they used earlier in the movie. The water from the waterfall now is going up the cliff! They have just put it in reverse.
Revealing mistake: When Will Smith throws a rock at the escaping Edgar alien, if you watch the rock after it hits the alien, it disappears after hitting the ground. (01:23:20)
Revealing mistake: When Batman places the heaters around the telescope to thaw the ice, the frozen floor moves like plastic when he places the second heater. (01:45:00)
Revealing mistake: When Sarah is making her way to the baby Stego, just before she gets on her belly and crawls closer to it, you can see the kneepads she has on.
Revealing mistake: At the end of the Sub-Zero vs Scorpion fight, Liu Kang jumps over to help Sub-Zero and Scorpion teleports away. A few moments later you see a shot where you see all the actors, (Liu Kang, Sub-Zero and Kitana), if you look closely you can see Scorpion waiting in the background just waiting to pop up and snatch Kitana.
Revealing mistake: Right after they "create" Leeloo and she is lying in the plastic cage with the little straps on her, the guy approaches her and says, "if you want out, you are going to have to work on your communication skills." She gives him a dirty look, and then you can see a huge hole, pre-cut in the glass, that she busts her hand through. (00:29:47)
Revealing mistake: In the scene with the helicopter chasing them down the street, apart from the fact that the rotors should catch on something and hurl the machine into a wall, when it finally hits the wall at the end, the pilot and crew quite clearly become about 4 crash-test dummies. This wouldn't be so bad if it weren't for the fact that they are unpainted and all sit in their seats looking straight ahead with their hands in their laps while they are driven into a wall. You'd think they could have at least posed the arms over their faces or SOMETHING!
Revealing mistake: When they are learning how to throw knives, the guy gets one thrown through his hand. If you watch this carefully, blood starts coming out of his hand before the knife hits. (00:28:45)
Revealing mistake: The whole time during the president's escape from AF1 (the scene where he's fighting with his corrupt agent) you can see through the airplane door that there is a loop in the movement of the water. It moves for about a second, and then stops, etc., etc.
Revealing mistake: When the boys go into the bear cave and all of the snakes are hissing, you can clearly see that one of the snakes is a rubber snake with a black stick attached to its head - the black stick is coming from a whole in the ground. It is not even a good snake, the 97 cent 'convenience store' variety.
Revealing mistake: After Dante's Peak explodes for the final time, the pyroclastic cloud rolls down the mountain toward the town. Harry shouts "Don't look back, kids, don't look back." and then we are shown a wide shot of the truck zooming down the ash-choked streets. Unfortunately, it's painfully obvious that this is either a miniature or CGI shot, because the truck isn't leaving any tracks behind it or trailing any clouds of ash despite its high speed. (01:28:19)
Revealing mistake: There is one scene where Alicia Silverstone is being taken away, and in the window, in the background, you can see a metro train with the letters on the side stating BC Transit and a picture of the British Columbia flag. Yet, the whole movie supposedly takes place in Washington state.
Revealing mistake: When Hillard throws the basketball at Ripley, you can clearly see the white tape on Ripley's hand which was used to catch the ball. (00:23:10)
Revealing mistake: Near the end of the film, when Bruce Willis is trying to escape into the Metro station, he swipes his fare card through the turnstile reader upside down - you can see the magnetic strip is visible above the slot. It still works anyway. (01:45:30)
Revealing mistake: When Captain Binghamton is giving his pre-invasion speech, the camera pans back and past a machine gun. The cartridges in the belt are just casings with no bullets in them.
Revealing mistake: During the ending sequence, just as J.T. Walsh is pushing the truck on the bridge, there is a shot looking at the front of the semi and you can see that it is not J.T. Walsh driving. The stunt man is noticeably heavier than J.T. is, and his hair is messier.
Revealing mistake: Though it may be a little hard to see, when Poe is in his prison cell towards the beginning, he is doing handstand pushups. This would be really cool to see a star doing these only, you can see the strap around his foot holding him up. (00:07:25)
Revealing mistake: In the big speedboat scene near the end, when Cage is hanging off the side of the boat the stunt double is obvious in wide shots, where the entire boat is visible from above. He has big long sideburns, which are in stark contrast to Cage's short hair, visible in closer shots. At various other points in the movie, stunt doubles appear of much different physical builds than the two actors, with markedly different hair colours, and I seem to recall that at least one of them had facial hair.
Revealing mistake: Towards the end of the film, a Cobra helicopter is flying in to assist with the extraction of the Navy Seals. There is a three-quarter frontal shot of the helicopter, one bank of rocket tubes can be seen to be empty; a few moments later, it's firing rockets from banks on both sides.