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: There is just too much movement and detail in the synthetic skin masks. Peyton lost a large portion of his face in the explosion, and cannot make much expression with his own face, but somehow he can make the masks move perfectly just like a real face.
Deliberate mistake: After the first scene where Hannah's ex-husband walks in without knocking and picks up the kids, Hannah is looking at some family pictures including her, her ex-husband, and the kids (supposedly taken when they were still married). But in the pictures they're all wearing the exact same clothes that they were in the previous scene. Could be a coincidence but that seems doubtful.
Deliberate mistake: When the terrorists shoot a man in the church and he falls on his back, both benches behind him topple (in the shot from the ceiling of the church). You can't see that the benches are connected and even if they were, the bench he doesn't actually touch wouldn't topple. (00:07:35)
Deliberate mistake: When King Willie is confronted by the Predator in the alley the Predator approaches him cloaked stepping through the puddle of water. You can see his footsteps causing the water to splash up. However, you can see the water splash up and go through his foot. The Predator is only cloaked, not intangible so the water should have splashed upon his foot, not go through. Water against his foot would be visible too, even though he is cloaked. (00:47:45)
Deliberate mistake: When the heads of the families assemble in the Palazzo Azzuro in Atlantic City and get attacked from a helicopter the rotors make the glasses on the table shake and the piles of fruit in the bowls collapse. As the Palazzo looks like quite a solid building this effect is a bit exaggerated. (00:59:35)
Deliberate mistake: It would be impossible for anyone to push up on a casket lid six feet underground and make the lid move much less crack enough to get their whole body through, the dirt would fill the box and trap the occupant.
Deliberate mistake: Towards the end of the movie, when Van Damme and the Sandman are fighting in the boiler room, the Sandman gets kicked into an open furnace for some time and then jumps out covered in flames. It's noticeable that he still has a full head of hair, which is impossible. Hair would be the first thing burnt right down to the scalp within a matter of seconds.
Deliberate mistake: When Steven Seagal and Kelly LeBrock are in the jeep, being chased through some fields by the cops, some of the shots of the jeep are flipped. Note the bullet holes on the windshield switch sides, as does the driver/steering wheel, the windshield wipers and the front license plate. As an aside, also note the numbers/letters on the license plate that have been altered via CG in the flipped shots.
Deliberate mistake: The elevator operated by gremlins starts ascending at around 5 stories per second, based on the floor readings. Yet when the elevator suddenly stops dead, Kate does not fly into the air caused by the huge speed change. (00:50:05)
Deliberate mistake: When the crew are piling into their jeep to ride out to their aircraft, the gunners ask the officers what their target is, and are disgusted to hear that it is Bremen, a tough one. The gunners should know their target already. Gunners were briefed on their target, and told what kind of fighter opposition to expect.
Deliberate mistake: Morse code takes a lot longer to type out than the captain of the Dallas seems to need. Likely "compressed" because otherwise the process would be quite dull, but still.
Deliberate mistake: In the hotel bar at night, when Edward is playing the piano and Vivian goes to find him, after Edward has dismissed everyone else from the room Vivian sits on top of the piano and puts her feet on the keyboard. Her feet go onto the keys in the middle of the keyboard but the sound that comes out is from the bottom and the top notes of the piano.
Deliberate mistake: When Bastian comes running up the stairs by the harbour, you can see a black couple on the right. The woman is wearing a grey coat with a black vest and a white shirt. The man is wearing a black coat, black shoes and white socks. When it cuts to Bastian running across the street, you can see the exact same couple wearing the exact same clothing crossing the street, but this time they are not walking together. The extras were used twice. (00:11:10)
Deliberate mistake: Kathy Bates gives James Caan his Noveril a number of times, but one particular time Kathy gives him his Noveril and leaves the room. When the camera shows James Caan holding the capsules between his thumbs and forefingers, it is apparent that they are not James Caan's hands in this shot.
Deliberate mistake: The same shot of the railway station concourse is used when Graham and George are heading to work, and also when George commits suicide. The giveaway is that several people are seen in the same position. (00:05:00 - 01:20:30)
Deliberate mistake: When Andy opens the tap to the liquid plastic it is that some of the liquid squirts on his hand. That would hurt and stain, but Andy doesn't seem to care... (01:14:35)
Deliberate mistake: When Robocain tries to use his chaingun on Robocop and it isn't armed, he snatches the remote unit from the OCP psychiatrist. If you look carefully, the remote unit changes from real to animated as soon as he grabs it.
Deliberate mistake: During the train sequence at the end of the film in 1885, it is blatantly obvious that the train is not going the speed that the DeLorean's speedometer is showing. In some shots, the train looks as though it is going little more than 20mph. (01:38:55)
Deliberate mistake: While Cohagen is on Mars, he calls Richter and chides him for trying to kill Quade. Richter is in a car on Earth, yet they're having a real-time conversation, which is impossible because of the distance. [While this is true, a movie with 4 to 21 minute pauses between lines would take rather a long time].