Mathilda May had rubber soles glued to the bottom of her feet in order to avoid cutting them during the scene in which she walks out of the building, after breaking the glass windows.
For her audition as Space Girl, Mathilda May had to learn her lines phonetically because her English was very poor at the time. In fact, when she was asked to disrobe, she excused herself to call her manager first, afraid that she was auditioning for a pornographic movie; it wasn't until she was assured that it was for a science-fiction movie that she relented. During the six months that May spent in London, England on this movie, she learned how to speak English, and even picked up a London accent.
Tobe Hooper's Director's Cut was two hours and eight minutes, then the movie was cut down to one hour and fifty-six minutes, the cuts being mostly scenes set on the spaceship Churchill. The original unedited European version contains more violent and erotic footage, which Tri-Star Pictures cut from the domestic U.S. version. It also contains the full Henry Mancini score, in place of the occasional Michael Kamen music cues placed at the last minute for U.S. prints. This version is now available on video, and runs one hour and fifty-six minutes.
Tobe Hooper came up with the idea of using Halley's Comet in the screenplay, rather than the asteroid belt, as originally used in the novel, as the comet was going to pass by Earth one year following this movie's release.
Tobe Hooper once revealed that in the early stages of shooting they waxed Mathilda May's pubic hair off completely thinking it would make her look less nude. It didn't. In fact it was worse because then her vulva was exposed, making her look even younger. So they had her grow a bikini strip of pubes back. May had to frequently remove her pants and panties to allow Hooper to "inspect" her. Make up artist Sandra Exelby talked about it in an interview: "We had this big discussion about Mathilda May. He [Hooper] said I want all her body hair off. And I said, 'You can't do that Tobe.' She's a young girl. At the time she was 18. 90% of the film she was on-camera nude while walking about. You cannot take all the body hair away. He said, 'Well I want the pubic hair as short as possible. And lighten it up. I don't really want to see it.' So every morning I was on my knees trimming and coloring and making it all look perfect." In some cases, Exelby didn't actually cut it, but simply sprinkled some hairs cut from wigs around May to satisfy Hooper.