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.
Continuity mistake: When Arnie is giving his info about what his Mars woman should be like, there are two things to look at on the screen in front of him: The screen zooms in on the woman's face, cuts back to Arnie, cuts back to the screen when it zooms in on the face again. Also, look at the sequence when he's selecting her personality: "demure" is lit up before he mentions it.
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.
Continuity mistake: When Quaid finishes Gary and his fellow agents, the concrete wall behind him shows a bloodstain. The only opportunity for it to appear there would have been as Quaid hits the moustache man in the face; but this guy stands up again, and it doesn't look like he cracked his skull (which would have caused a stain).
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.
Continuity mistake: When Arnie enters the hotel room on Earth, he receives a phone call from a man with a suitcase who tells him to look through the window. While Arnie is approaching to the window, we can see in the display that the mysterious man is looking to his upper right. In the next shot, when Arnie is looking through the window, we can see that the hotel room is located at the man's left side.
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.
Continuity mistake: Arnie has come back to the apartment after shooting his coworkers and asks Lori if this is a hallucination. He then reveals fresh blood smeared all over the palms of his hands but he had grabbed her before he asks the question. Lori is sitting in front of him without a drop of blood on her.
Continuity mistake: When Quaid uses the hologram, it's a mirror image of himself. However, before he enters the reactor room full of guards, we see him put the hologram device on his left wrist. His hologram (the one all the guards shoot at) has the device on his left wrist as well, instead of what would be the right.
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.