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Despite releasing a new version of the movie titled "Alien: The Director's Cut" in 2004, which is preceded on the DVD/BluRay version by a short introduction where Sir Ridley Scott explains his choice of making this version, Scott wrote in a separate statement in the movie's packaging that he still feels the original Alien (1979) was his perfect vision of the movie. The newer version is titled "The Director's Cut" for marketing purposes, featuring deleted scenes many fans wanted to see incorporated into the movie (such as the scene where Ripley discovers the Alien nest). He also deleted as much material from this cut to maintain the movie's pacing, resulting in a new version that is actually one minute shorter than its original (much like his Director's Cut of Blade Runner (1982) was also shorter than the original version).
The blue laser lights that were used in the alien ship's egg chamber were borrowed from The Who. The band was testing out the lasers for their stage show in the soundstage next door.
The chestbursting scene was NOT filmed in one take (despite the myth). The scene was filmed twice: on the first take, the chestburster was unable to cut through Kane's shirt, so the crew needed to reset and shoot it again. The failed attempt is visible in the finished film, since director Ridley Scott thought it made it look like the creature was struggling to push its way out, and made the scene more violent (see The Beast Within documentary where this is discussed). According to designer Ron Cobb, the two takes of the scene were shot from multiple angles, and about 40 minutes of footage was available for screening.
Shredded condoms were used to create tendons of the beast's ferocious jaws.
According to Yaphet Kotto, Sir Ridley Scott told him to annoy Sigourney Weaver off-camera, so that there would be genuine tension between their characters. Kotto regretted this, because he really liked Weaver.
To get Jones the cat to react fearfully to the descending Alien, a German Shepherd was placed in front of him with a screen between the two, so the cat wouldn't see it at first. The screen was then suddenly removed to make Jones stop advancing and start hissing.