Alice Cooper used the bike impalement trick in his stage shows prior to this movie. The bike he uses was his own personal prop.
John Carpenter's first film that he made independently since Escape from New York (1981). Not only because of the box office failure of his previous film Big Trouble in Little China (1986), but also his frustration with working with the studios.
(at around 25 mins) When Dr. Leahy introduces himself to Dr. Birack, Peter Jason wasn't expecting Victor Wong to walk away in the middle of the scene. Jason's subsequent confused appearance and awkwardness is natural and unscripted.
John Carpenter states he set out to make a film that was atmospheric and dreadful. At the time he was noticing a lot of derivative horror films and wanted to try something new involving quantum mechanics and religion.
The recurring dream was shot on video and filmed off of a television screen.