Ravenhurst is Roger Daltrey's real-life residence. Daltrey lent his mansion for use in the movie, on the condition that he co-star in it. The producers agreed, and thus the role of "Clive Jackson" was created for him.
Sam Elliott (Pete Danner) and Katharine Ross (Margaret Walsh) met and fell in love when they co-starred in this movie. They married in 1984 and are still together.
Two years after its release, Sam Elliott gave an interview to Jerry Buck of the Associated Press in which he said about this movie: "I wouldn't rush out to see it. It's about fifteen years behind its time."
John Coyne was asked to write a novelization in six weeks to promote the movie, and Hollywood spent a lot of money to make it "briefly" a best seller.
Considered for Karl were Harry Andrews, Peter Cushing, Bernard Archard, Herbert Lom, Donald Pleasence, Sir Christopher Lee, Michael Gough, Anton Diffring, Peter Arne, Patrick Troughton, Peter Vaughn, and Donald Houston.