The director was not fond of this movie when he finished filming it and seriously considered editing it down to a television episode. What changed his mind? The addition of the musical score.
The first American movie to show a toilet flushing on screen.
The director bought the movie rights to the book anonymously, then bought up as many copies of the book as he could to keep the plot a secret.
Inspired multiple sequels, a prequel and a TV series. Remade in 1998. Shot for shot. Leading many to wonder, why? It bombed.