The first use of computer digitized images as part of a feature film (not merely monitor graphics) was the Gunslinger's point of view in Westworld. After the process was finally developed enough to produce satisfactory results, it took a mere eight hours to produce each ten seconds of Gunslinger's pixellated POV.
Michael Crichton became inspired to write this film after a trip to Disneyland, where he saw the Pirates of the Caribbean ride, and was impressed by the animatronic characters. Furthermore, the ride is mentioned is Jurassic Park (1993), when Malcolm says the "Pirates didn't come to life and kill people", unlike what happens in this film. Jurassic Park (1993) was based on the novel by Westworld director Michael Crichton.
There were several minor injures during filming. During a shootout scene a piece of wadding from a blank cartridge struck Yul Brynner in the eye, scratching his cornea and leaving him unable to wear his light reflecting contacts without his injured eye turning red and tearing up, so shooting had to be maneuvered to allow time for his eye to heal. And during the scene where James Brolin's character was bitten by a rattlesnake, while the milked rattler was attached to Brolin's arm, he was bitten by the teeth on the snakes lower jaw, despite wearing padding on his arm made of leather and cotton.
Michael Crichton would later use the similar plot line about an amusement park that goes horribly wrong and the attractions malfunctioning for his novel "Jurassic Park", which would become the hit film Jurassic Park (1993) 20 years later.
After the filming of Terminator 3: Rise of the Machines (2003), Arnold Schwarzenegger was to produce and star in a remake of Westworld for Warner Bros. After that, he was meant to star in a sequel to Conan the Barbarian (1982), pairing him with a younger swordsman. Both these plans never came to fruition after Schwarzenegger was elected Governor of California in 2003.
Director / screenwriter Michael Crichton re-edited the first cut of the movie because he was depressed by how long and boring it was. Scenes that were deleted from the rough cut include the bank robbery and sales room sequences, hovercraft with passengers flying above the desert in the beginning, additional and longer dialogue scenes, more scenes with robots going crazy and killing guests including a scene where one guest is tied down to a rack and is killed when his arms are pulled out, longer chase scene with Gunslinger chasing Peter, Gunslinger cleaning his face with water after Peter throws acid on him. In Crichton's assembly cut there was also a different ending which included a fight between Gunslinger and Peter (which was deleted because it seemed like it was staged and foolish) and an alternate death scene of Gunslinger where he is killed with the same rack that was used by one of the other robots to kill one of the guests in previously mentioned deleted scene.