Continuity mistake: At the start of the movie when the gun store is being robbed, one of them fires a portable rocket launcher at the police car, causing it to roll over and spin. As it comes to a stop just outside the store, it's visible that the driver's side window has been blown out, and the vehicle interior is visible, however when the same guy prepares to fire the bazooka to finish it off, the window has returned and is completely intact.
Factual error: One of the brain surgeons says about Cain's brain, "it's nice and clean in here, there's no damage", except we see throughout the film Cain using the drug Nuke, even a new variation of it called Blue Velvet. When he injects it he's with his chemist Frank, and mentions two of its ingredients, "benzadrine and scopolamine" - no way his brain would be nice and clean.
Visible crew/equipment: When Robocop visits Cain's hideout and sends his car in as a decoy, after he returns to the car, watch the driving shot closely. A wire has magically strung itself across the entrance and attached itself to the back of the car - it wasn't visible from an earlier shot. As the car drives forward it stretches the horizontal wire, and just as a tiny amount of pressure is exerted, the car explodes. Yeah, it's technically a mistake, but I think it's more worth checking out just to see how those tricky effects are achieved.
Revealing mistake: Just before RoboCop gets out of the car to walk towards the baseball coach, Lewis shoots at the coach and he jumps back. Watch carefully. Whilst jumping, his hat comes off slightly and you can see the make-up for the hole in his head, which he doesn't receive for a few seconds after this. Seen best in Slow motion on the DVD. (00:50:31)
Continuity mistake: When RoboCop is in the street with his new directives, he shouts "Back" at Lewis and puts his hand down to take his gun out. We can see his hand going down beside his leg and then coming up with a gun, but his hand was nowhere near his leg, and even though we hear the leg opening sound effect, the leg never moves. The same sort of mistake happens after RoboCop 2 destroys the Nuke hideout. RoboCop is investigating, and afterwards puts his gun away. The gun goes down to his leg, but the leg never opens, yet the sound effect is played. Sloppy camera work is responsible for both cases, it should have been higher up.
Continuity mistake: When RoboCop gets out of his car in the scene where the baseball coach is firing at him, the building behind him is reflecting the sun and looks very bright. Less than 2 seconds later we see RoboCop walking towards the electrical shop and the building is very dull looking. Where did the sun go? (00:50:36)
Revealing mistake: When Lewis is shooting at RoboCop 2 she quickly runs as RoboCop 2 aims for her. He shoots at the car behind her, and if you look closely at the boot lid, you can see slight dents made by the crew so that they can make sparks come out of the boot when it is shot. (01:39:17)
Continuity mistake: When Caine's cronies throw the dismantled RoboCop out of the limo in front of the police station, take a look at the shot of the pile of parts. Both of his forearms are intact from the hand right up to the elbow. However, his right hand was blown off at the wrist just before he was "stripped".
Visible crew/equipment: When Cain and his gang are making their escape from the drug factory at the start, we can see a crew members hand very obviously poking out from behind the door frame, giving the actors their prompts when to go.
Continuity mistake: When RoboCop and Lewis go to deal with the baseball kids robbing the electrical store, they are shot at and Lewis spins the car round. We cut to a close up of the car and see Lewis get out, meanwhile RoboCop opens his door and puts his hand on top of the car, supposedly to get out. A few moments later he is still siting in the car, arms on his legs. So why did he put his hand up? (00:50:12)
Revealing mistake: When the mayor is sliding down the sewage drain, you can see some kind of a mat or something under him, probably to make him slide better.