Other mistake: As the Terminator is approaching Sarah in the Tech Noir nightclub, several other patrons can be seen behind her sitting in booths. These same people are in front of Kyle (he pushes them out of the way to get to Sarah before the Terminator does), yet he's on the other side of the club by the bar. (00:35:10)
Continuity mistake: When Sarah is sitting in the bar after talking with the police, there is a drink in a glass on the table in front of her. The scene cuts away and when it cuts back, it is a small bottle, not a drink glass. (00:33:45)
Audio problem: When the terminator smashes the car window, the crash sound occurs before his fist actually makes contact. (00:12:35)
Character mistake: In the final scene at the Mexican gas station there's a sign that says "cigaros" instead of "cigarros," which means "cigars" in Spanish.
Revealing mistake: Just after the Terminator breaks into the police station, he is firing his gun, when he fires it repeatedly he makes a policeman jump who is lying dead on the floor, look closely.
Continuity mistake: When Arnie says "I'll be back" and leaves the police station he throws both the doors open as he leaves one of them falls back into place but the other one stays open. When he drives his car through the window both doors are closed.
Revealing mistake: When the Terminator takes out his "fake" human eye, he looks into the mirror. It is very obvious it's a dummy: 1) He has unnatural movements. 2) His skin is a lot paler, and not shiny. 3) His hair style has changed. It's easier to tell in the following shot, as he looks closer to the mirror that he's changed back to "real." (00:59:55)
Other mistake: Why does the Terminator have a HUD (Head-up-Display) or a GUI (Graphical User Interface)? This is a stupid mistake in many movies with cyborgs or androids. A machine itself does not need a HUD. A HUD is an interface for humans to help us interact with machines. A machine does not need a graphical interface to interact with itself. A machine can interpret the reality around internally using machine code within its CPU using zeros and ones. There is no need to project a HUD in the eyes of the terminator. (of course it looks cool and the viewer gets the information that the Terminator is a machine, but in reality it would be - let's say - a stupid redundancy to build in a monitor into a camera).
Continuity mistake: When Arnie gets shot in the club after he gets up again there's no bullet holes in his chest or blood on his shirt. (00:35:50)
Audio problem: When the Terminator first arrives in 1984, the whole time displacement sequence (or whatever you want to call it) is witnessed by a garbage truck driver who mutters 'What the hell?'. His mouth however is obviously saying something else which has been dubbed over. (00:04:00)
Continuity mistake: Throughout the car chase shots where the Terminator is in the stolen police car, the car's rear view mirror is round. After the car crashes into the wall in the tunnel, the rear view mirror is square. (00:49:35 - 00:50:20)
Continuity mistake: Just before Kyle exits the car park, he rams the police car driven by the Terminator into a parked car, and you can see the front left corner of the police car is damaged. In the next shot when you see the police car exit the car park, the damage has gone. (00:48:30)
Continuity mistake: When The Terminator is searching through Sarah's address book in his apartment he has flies on him. There is one on his forehead, but when the janitor knocks on the door, the Terminator turns his head towards the door and cusses at him but there is no fly on the forehead. When he turns back and continues reading the fly is again on his forehead at the same exact place on the forehead. (01:14:05)
Continuity mistake: Early in the movie, prior to heading out to the bar where she first sees the Terminator, Sarah Connor is holding her iguana at her apartment while talking to her roommate. In the first shot, she is holding it with her left hand under the lizard's chest. The film cuts to a different angle, and now the lizard is resting against her shoulder, with Sarah's left hand on its upper back. It cuts back to the original angle and again her hand is supporting the chest. (00:23:25)
Continuity mistake: In the scene where Arnold is turning off the power in the police station he gets shot by a cop and jerks forward. But every other time he is shot he does not even twitch. (01:00:55)