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)
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)
Revealing mistake: Just before the reporter and cameraman are killed on top of the van, a woman is running away from the scene and is shot in the legs, and she falls to the ground. A man comes to pick her up and he gets shot in the back. If you look carefully, you can see the marks that the vest he is wearing make on his back, (which explodes under his clothes making it look like he was shot). (01:39:25)
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.
Revealing mistake: When Robocop finds Hob shot and dying in the back of the truck there are close-ups of Hob lying on piles of the drug money. In one shot the $50 bill on the top of a stack of bills is lifted at the corner and you can see that the bill under it is blank paper.
Revealing mistake: During several of the scenes, when people are shot; some of the impacts are accompanied by blood splatter, others just look like squibs that weren't filled with blood.
Revealing mistake: After Robocop kills the man holding a baby, one can see the baby is a doll.
Revealing mistake: When the truck drives through the bar, the brick walls are a blatant thin piece of painted cardboard.
Revealing mistake: After Robocop goes through the windshield and grabs Cain, leaving the driver seat empty, in the long shot the stunt driver can be seen.
Revealing mistake: When the baseball coach is exchanging fire with Lewis, he reacts to a close impact. As he does, his arms brush his cap, and the makeup for the bullet wound on the upper left side of his forehead is revealed. When the fatal shot is fired, his cap is down in position again.
Revealing mistake: When Robocop punches through the door at the nuke lab it appears that one thickness of the door was removed ahead of time. When the guy looks through the sliding peep-hole it's obvious that the door is thick. But especially after Robocop removes his arm you can see it is only single thickness and you only see the shiny inner of the door peeled inwards and none of the brown paint from the outside.
Revealing mistake: When Robocop is on the bike, he does a skid. in the exact place where he does this, there is already skid marks from previous takes.
Revealing mistake: The Mayor looks into the armoured van at the money, and picks up a gold bar. It looks bad, is obviously too light to be gold, and doesn't clink when put back.
Answer: We're never given specifics about it, but we do know it's the most addictive drug in history.