While serving as executive producer, author Whitley Strieber, whose experiences serve as the basis of the film, expressed concerns about Christopher Walken's abilities in portraying him. When Strieber finally told Walken that he might be portraying him as a little too crazy, Walken replied, "If the shoe fits."
Anne Strieber is referring to Joseph Campbell's four-volume compendium of World Mythology with her "Masks of God" observation.
The opening shots of NYC were done by an independent cameraman allowed to fly around NYC in a helicopter using a time lapse camera.
The scene in which Strieber laughs when he sees the visitors was Christopher Walken's natural reaction at seeing the alien designs and thinking they looked silly. Director Philippe Mora liked his reaction, thinking it made the scene more disturbing and kept it in.
Director Philippe Mora wanted star Christopher Walken involved in the casting of whomever played 'Anne Strieber'. It was Walken who suggested Lindsay Crouse.