Plot hole: When Arnie is taking off his woman's head he presses a switch by the ear and the ear comes out. The device reaches right inside the fake head and there would be no room for Arnie's real head. (00:46:00)
Continuity mistake: During the chaos that ensues after Richter shoots out the spaceport windows, one of the rebels clings to a yellow pipe before being sucked into Mars' atmosphere. His hands are varying distances from each other, depending on the shot. (00:46:50)
Revealing mistake: When Arnie blows the old lady disguise mask on Mars Immigration, they shot him and the dome crashes. Right after the soldier gets sucked out of the room, some extra comes rolling and kicks the camera. (00:47:05)
Continuity mistake: In the scene where Quaid unfolds a flyer for The Last Resort, he unfolds it with the flyer image facing the camera. When the scene cuts to him looking at it, the flyer image is facing him. (00:52:00)
Audio problem: Just after Arnie accepts the cab driver's offer and the other one complains, Arnie's driver gives him the finger and says something like, "Eat this", but his lips don't match what he's saying. (00:52:45)
Continuity mistake: When Arnie meets Bennie, he takes him to his cab and opens the door for him to get in. At that time, there's an explosion, and Bennie pulls the door down to shield himself and Arnie. The camera switches to behind them, and Bennie is just now pulling the door down. (00:52:50)
Continuity mistake: A few minutes before Quaid kills his "wife", there's a shot of her with bright pink lipstick. Immediately before he shoots her, her lipstick is burgundy. (01:03:10)
Continuity mistake: When Melina comes to the rescue of Doug, she starts shooting his captors. He drops to the floor, then in the next shot, he drops again. Doug also wakes up on top of a dead guy who had landed much further away from him before. (01:04:15)
Revealing mistake: When Quade shoots Dr. Edgemar, Lori yells "Now you've DONE IT.", and the wall explodes, which is plainly made of foam. Many of the pieces of 'wall' tumble lightly across the floor. (01:05:40)
Continuity mistake: When Doug and Melina are being chased by Richter they leap from the catwalk in the big dome. When they reach the other side, from one camera angle, they grab the horizontal bar on the dome scaffolding. From the next angle they are holding onto the diagonally vertical bars swinging inward. (01:06:30)
Continuity mistake: In the scene where Michael Ironside's cronies are dragging Arnie to the service lift, watch Arnie's head: It changes from being flexed forward to being extended backwards as they swap camera angles. His hand positions change as well from shot to shot. (01:06:40)
Continuity mistake: During the hallway fight sequence between Lori and Melina, we see Quaid in the background aiming a machine gun - just as Melina gets kicked in the back. But a few seconds later, Quaid reaches for the same gun a second time. (01:07:40)
Continuity mistake: In the scene where Quaid takes out Lori with a bullet to the head, she lands on the floor in such a manner that allows blood to run across the right side of her forehead. A few shots later Melina pushes Lori out of the way, repositioning the body on its opposite side. But once Richter discovers Lori moments later, blood is only visible running across the left side of her forehead. If anything, there should be blood running from either side of the bullet wound. (01:08:10 - 01:09:05)
Visible crew/equipment: When Quaid and Melina hop into Benny's cab and are being chased by Richter, watch Benny. During the shots where the perspective is from behind Benny, you can see that it is a stunt driver in the car. His head is shaved neatly, yet Benny's hair is curly and frilly all over. (01:11:00)
Continuity mistake: When Quaid enters George/Kuato's private room in the rebel base you can see George's desk has a different arrangement from one shot to the other with Quaid's gun disappearing, a blue container swapped with a white on, the computer's screen having a cable plugged in or out and other objects moved around. (01:16:00)
Continuity mistake: In the airlock where Benny fires his machine gun at George, the lock handle behind Benny rotates on its own. (01:23:05)
Continuity mistake: In the scene where Quaid and Melina are strapped into chairs by scientists, Quaid breaks out and stabs a bar into a guy's head using a downward motion. In the next shot, the bar is now coming up from the under side of the scientist's face and out of the top of his head. (01:30:00)
Revealing mistake: Doug has the hologram when inside the alien nuclear reactor, and a bunch of bad guys encircle the holographic image and fire at it at point blank with automatic weapons, and not one bad guy gets hit. If they encircled the 3D image, at least a few bad guys would have been hit by their own men. (01:37:00)
Continuity mistake: When Arnie uses the hologram projector in the alien reactor, there is a brief shot of him facing his own hologram image. Note that the gun and the projector switch positions in Arnie's hands - the bloodstain on his shirt's sleeve does not. (01:37:55)
Continuity mistake: When Arnold Schwarzenegger and Rachel Ticotin are being attacked by the giant drilling machine, Arnie grabs a pneumatic drill and cuts the main oil line of the machine, getting the left side of his face and his shirt doused in oil. Yet throughout the remainder of the film, there is no oil on Arnie's face or shirt. (01:39:55)
Answer: Verhoeven points out that if a viewer believes the whole film is a dream, then Edgemar's prediction that Quaid will end up being lobotomized is fulfilled in the fade to white which ends the movie.