From The Grindhouse Cinema Database
- A poster for Four Flies on Grey Velvet is visible in the lobby of the theatre: it's the title of writer/producer Dario Argento's third film.
- The building used for the exteriors of the Metropol theater still stands in Berlin. It's a club called Goya that's been host to several horror conventions thanks to its appearance in this film.
- Lamberto Bava cites this as his personal favorite of the films he has directed.
- The Playstation video game 'Silent Hill' pays homage to this film as a theater called 'Metropol' can be seen in the game, along with posters advertising this film at the box office.
- All of the graphic violence in the film was fully scripted and little improvisation was done on screen.