It is often incorrectly stated that Demi Moore was pregnant in real life during the filming of this movie. Production wrapped in August 1987 and Rumer Willis wasn't conceived until November. Moore confirmed this in 2019 by posting behind-the-scenes Polaroids on Instagram of her putting on the prosthetic belly and fake nipples ahead of filming.
Ellen DeGeneres filmed a small role, but it was cut from the film before release. The cut scene was shown on Ellen: The Ellen DeGeneres Show (2003) on 5/23/07. Had it not been cut, it would have been her first film role.
The meaning and relevance of this film's 'The Seventh Sign' title is that it refers to the seven seals which feature in the final book of the New Testament of the Bible: The Book of Revelation.
Demi Moore and Michael Biehn both later appeared in the documentary about Down Syndrome actor John Taylor--who appears in this film--entitled Yours to Keep (1989).
The first theatrical feature film in which Demi Moore had sole name-above-the-title top first billing.