Quiz

Many fans were upset with the 2004 DVD release from Sony Pictures Home Entertainment. The cover was completely different, and a disco score played over the opening credits, instead of the original atmospheric piano piece. In 2009, Anchor Bay/Starz Home Entertainment re-released the DVD using the original poster as the cover, and restored the original music over the opening sequence.

Most ads and posters for the film carried a photo of a young man about to be impaled with a skewer of meat and vegetables, with the slogan "John will never eat shish kebab again". However, there is no character in the movie with this name.

The brain surgery was performed by a real neurosurgeon on a fake brain.

Glenn Ford and assistant director Charles Braive were involved in a dispute on set in which the actor allegedly hit the AD. In an interview with "The Terror Trap", producer John Dunning said, "He hit our AD, who had called a lunch break in the middle of one of Glenn's scenes. I had to stop the police from arresting him. It was a mess. Glenn wouldn't come out of his dressing room until the first AD apologized, who said he would never apologize to Glenn. But I told him that this might be the end of his career as an AD if he didn't. So, he went and said he was sorry . . . and Glenn said he was sorry. They kissed and made up. As far as I know, Glenn never hit anybody else".

Many posters for the film utilized a marketing gimmick that had been used for Alfred Hitchcock's Psyco (1960). They featured a warning that read: "Because of the bizarre nature of the party, no one will be seated during the last ten minutes . . . Pray you're not invited".