Shirley MacLaine turned down the lead female role in The Exorcist (1973) in order to make this movie.
Perry King credited Shirley MacLaine for helping him with his performance in this movie. Being only his second movie role, MacLaine took the budding yet serious young actor under her wing during the production.
Pre-dating the release of The Exorcist (1973), this movie is considered amongst genre fans to be one of the first movies to deal with the theme of possession.
The first movie starring role for Perry King (Joel Delaney).
Two of the crew members were major figures in the development of Sesame Street: score composer Joe Raposo wrote most of the show's songs in its early years, and screenwriter Matt Robinson originally played Gordon and was one of the show's founding writers.