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James Cameron got the idea for the film during post-production of his previous film, Piranha II: The Spawning (1982), in Rome. Since he had been fired from the production, he had spent the last of his own money on the plane ticket to get there, hoping to be at least involved in the editing process. Without money for proper food, he became increasingly sick, and went to bed one night with high fever. He had a nightmare of a metal endoskeleton emerging from flames, dragging itself over the floor holding kitchen knives. When he woke up, he immediately made a drawing of this vision. Most of the script was written backwards from there: the endoskeleton would have to be futuristic, but since Cameron couldn't afford to set the film in the future, the solution was to bring the future to the present, hence the 'time travel' aspect of the script was written in. When special effects artist Stan Winston was brought in, he added a few more designs for the endoskeleton, but in the end they basically used the one that Cameron had drawn the first time.
While shooting this film, James Cameron often resorted to what he called "guerilla filmmaking" as a way of getting around acquiring permits needed to film certain scenes. This involved the production crew and actors quickly arriving at a specified location, shooting the scene and leaving before the police arrived. As a result, some of the people seen in a few shots are actual everyday citizens completely unaware they're in a movie. This was also used for re shoots with Cameron even calling and waking Arnold Schwarzenegger once at 3am to meet him at a location already in full costume to quickly re-shoot a scene. Cameron also used this tactic to film the very last scene where Sarah drives off into the desert. Waiting for the heat to rise to the point that ripples could be filmed a highway patrolman appeared. Producer Gale Ann Hurd convinced him they were working on a UCLA film project and he allowed them to finish.
Arnold Schwarzenegger worked with guns every day for a month to prepare for the role. The first two weeks of filming he practiced weapons stripping and reassembly blindfolded until the motions were automatic, like a machine. He spent hours at the shooting range and practicing with different weapons without blinking or looking at them when reloading or cocking. He also had to be ambidextrous. He practiced different moves up to 50 times. He wound up garnering a compliment in "Soldier of Fortune" magazine for his realistic handling of the guns on camera (whereas the magazine usually lampoons movies for their inaccurate depictions of weapons use).
Arnold Schwarzenegger tried to avoid Linda Hamilton and Michael Biehn as much as possible since the Terminator was trying to kill them, not form connections.
(at around 23 mins) Near the beginning of the movie, when Sarah Connor (Linda Hamilton) receives a message on her answering machine breaking her date, the voice on the machine is James Cameron's. Years later, Hamilton and Cameron got married and subsequently divorced.
James Cameron got the idea of giving Arnold Schwarzenegger even fewer lines in the film than Schwarzenegger's earlier film Conan the Barbarian (1982), in which Schwarzenegger only had 24 lines. In this film, Schwarzenegger has only 14 lines.
William Wisher: (at around 38 mins) The co-writer of this film plays the police officer who attempts to assist the Terminator after he is thrown from the hood of the car, but gets knocked unconscious for his trouble. Wisher has a cameo in the sequel Terminator 2: Judgment Day (1991) as well, where his character seems to have a look of recognition upon seeing the new Terminator.
James Cameron: Cameron's voice is heard three times in the movie: as Sarah Connor's date on the answering machine and twice as a manager of Tiki motel, who is heard (but not seen) speaking to Sarah and then again answers the phone when The Terminator calls.
James Cameron: [Biehn's hand] (at around 42 mins) Michael Biehn's character gets bitten on the hand by another character. See Aliens (1986) and The Abyss (1989).