Shooting was delayed while actress Elisabeth Shue recovered from an torn Achilles tendon sustained during filming.
An anatomically correct, totally working computer model was created of Kevin Bacon's entire body - down to the last capillary. The 3D model has since been donated to scientific researchers.
The tranquilizer guns used in the beginning are in fact PGPs, a very late model paintball gun. A scene depicting the invisible Sebastian brutally raping his neighbor, then climbing off her as she wept was deleted because test audiences, still identifying with Sebastian, seemed to feel it was too early in the movie for him to have descended to that level of evil. Other deleted scenes included Sarah discussing with Linda and Matt the possibility that Sebastian had fondled her, Sarah confronting Sebastian about the death of the dog, and Linda being stalked by Sebastian. The latter two scenes contain footage that was used in the promotional trailers.
Elisabeth Shue's character's surname, McKay, is the same of her last character, Molly McKay, from "Molly".
Source: IMDb.com
The 'underground laboratory' set, constructed in Culver City, CA, is among the largest ever constructed.
Some of the film was shot atop the
U.S. Department of Labor building in Washington D.C.
Source: rottentomatoes.com