In the DVD commentary, director Armand Mastroianni said that horror fans frequently confuse this film with When A Stranger Calls (1979), because of their similarly threatening titles. Mastroianni also said coincidentally, 'He Knows You're Alone' and 'When A Stranger Calls' were both playing at a New York City theater at the same time. He said that the theater marquee read 'When A Stranger Calls He Knows You're Alone' as if it was all one big movie title.
According to Armand Mastroianni and Scott Parker, the film had numerous working titles throughout the production. Among them were Blood Wedding, Shriek, and The Uninvited. It was the studio that finally attached 'He Knows You're Alone' to the film, after it tested well with audiences.
For years it was believed that Pat Benatar's hit song "Hell Is For Children" was featured in the film's soundtrack. The song, however, is never heard throughout the film, nor credited on the closing titles.
Tom Hanks later described the preposterousness of the carnival scenes on Late Night with David Letterman (1982), noting how ridiculous it was to depict the rides being 'enjoyed' by patrons in freezing temperatures.