"The Fly" was originally a story by George Langelaan that appeared in the June 1957 issue of Playboy magazine.
Michael Rennie was offered the title role but declined it because his head would be covered thru most of the picture.
James Clavell's first script was faithful to George Langelaan's original story, but Fox executives demanded a happier ending.
Patricia Owens has a real fear of insects. Director Kurt Neumann used this by not allowing her to see the makeup until the "unmasking' scene.
In the scene where the fly with Andre Delambre's head and arm is caught in the spider's web, a small animatronic figure with a moving head and arm was used in the spiderweb as a reference for actors Vincent Price and Herbert Marshall. Vincent Price later remembered that filming the scene required multiple takes, because each time he and Herbert Marshall looked at the animatronic figure, with its human head and insect body, they would burst out laughing.
Part of the laboratory set was Emerac, the computer from Fox's production Desk Set.
That is actually David Hedison, not a stuntman, inside the Fly makeup. Filming lasted mid March-mid April 1958.
The lab set cost only $28,000 and included some surplus Army equipment.
The teleportation that causes Andre and the fly to switch atoms is never seen.
This became the biggest box office hit for director Kurt Neumann, but he never knew it. He died a month after the premiere, and only a week before it went into general release.
This was such a success at the box office that it became one of Fox's biggest hits of 1958.
Uncredited producer Robert L. Lippert was able to make additional money from the success of this film. His own company, Regal Films, produced Space Master X-7 which 20th Century Fox used as the cofeature for this film.