According to director Nobuhiko Ôbayashi, this is the first Japanese film to use video effects, which he applied in a scene to make one of the girls "dissolve" underwater through low fidelity video and a simple chroma key effect.
None of the seven young actresses who portray the group of friends who visit the house was a trained film actress. The young ladies were models who had worked with director Nobuhiko Ôbayashi in advertisements or commercials.
The script was partly inspired by Obayashi's then 12-year-old daughter Chigumi. She told him of a fear she had, that the mirror she used would eat her.
Between the time that the project was given the green light by Toho, and when the film was completed, director Nobuhiko Ôbayashi produced several successful projects based on the story. He turned it into a commercially-successful manga and radio drama; he also spun off a number of product tie-ins before the film was ever released. Obayashi did this because he wasn't Toho's first choice to direct the project, as they felt he wasn't experienced enough to handle a special effects heavy film. However, practically all of the director's Toho had under contract refused to do the film, as they all thought the script was awful and believed that their careers would be hurt by making such an exceptionally bizarre film. Once the tie-ins became successful, Toho eventually let Obayashi direct, bypassing the traditional hiring system.
Shortly after this film's release, Obayashi proposed a story for what would have been the 16th Godzilla film. Had that film been made, it would have used the same crew as this film, with Godiego once again providing the music. This story told of a little girl named Momo who discovers the dead body of Godzilla. After being dissected, Godzilla is revealed to be a pregnant female alien named Rozan who died of diabetes. The brain of the dead Rozan instructs the humans that she must return with her unborn son to the planet of Godzilla, so her body is converted into a spaceship. The newborn child would be reunited with its father and they would have fought a female monster that shot fire from her breasts. Ultimately, this project was discarded by Toho and was instead released as a short story in the Japanese edition of Starlog magazine; the artwork was by future Akira director Katsuhiro Ôtomo. The story lists the credits as if it was a feature film, with Obayashi as director.