George Lucas loved the old Universal Flash Gordon serials as a kid, and wanted to make a modern version based on the original comic strips. Federico Fellini was optioning the rights at the time, so Lucas wrote Star Wars: Episode IV - A New Hope (1977) instead.
In the finished film, George Harris' dialogue as Prince Thun of Ardentia was dubbed. His voice is on the Queen soundtrack album, indicating that the change must have been made fairly late in post-production.
Dino De Laurentiis had never heard of Queen before making this film. The band was approached for the gig in 1979, and they were immediately interested. Their manager arranged a meeting with De Laurentiis to discuss the opportunity, and he allegedly asked, "Who are the Queens?"
According to Sam J. Jones, while filming the tilting-disc fight scene, the actors would get covered in paint by the disc that was spray painted silver. They would have to take extra time between each take to wipe silver paint off their bodies.
In the original script, when Flash is sentenced to death by Ming, Dale bursts out that Ming is "absolutely merciless". Ming is enthralled with the description, and immediately starts calling himself "Ming the Merciless".
According to an August 1981 interview in Starlog magazine, Dino De Laurentiis really wanted Kurt Russell to play Flash Gordon. Russell turned the part down because he thought the character lacked personality.
The actors playing the Hawkmen couldn't sit down because the costumes would hurt their backs. Melody Anderson told Starlog Magazine, "They could never sit down, because when they did the wings would dig into their backs. When we had a rest period, you'd see all these guys lying on their stomachs with wings, like they were ready to take off. It was a very funny sight." According to Brian Blessed, he had to sit on a perch.
John Hollis played one of Klytus' Observers, who was fitted with an electronic "imager" device in place of his eyes. Hollis also had a role in Star Wars: Episode V - The Empire Strikes Back (1980) as Lando Calrissian's aide, Lobot, who had a similar distinguishing feature: a cybernetic device installed over his ears.
According to Brian Blessed, it took about three days to prepare the Ajax sequence and put everything, including dozens of hanging Hawkmen, in place. Blessed put in his own special effects, going "pew pew pew" as he "shot" his cardboard bazooka. Because of this, they had to take another day to reset. Blessed didn't feel too bad, as Sam J. Jones was also a pretty hot hand with his prop gun, also filling in the "pew pew's"
For the scene in which Dale turns into a giant spider for a dream sequence, Melody Anderson spent six hours getting painted green, wearing fake eyes and fangs, with a head piece that weighed over 20 pounds. When Mike Hodges came in, he said, "This is wonderful, but we can't use this! It has absolutely nothing to do with the script."
CRAZY CREDITS: During the opening credits, each cast member's credit is accompanied by artwork of his or her character from the original comic strip. Therefore, you see all of the major characters as cartoons before you see the cast members who play them.
The script was translated into Italian by a woman, who Lorenzo Semple, Jr. described as a "horrible" translator. He gives an example, saying if it said, "The tall, beautiful woman walked into the room," she'd say, "Oh, what a beautiful cat." Semple complained, but Dino De Laurentiis said, "I do not want to be fooled by the words; I do not want to be fooled by written words. I want to know the story."
The movie came about when producer Lou Scheimer, seeking additional funding for his animated NBC movie of the week Flash Gordon: The Greatest Adventure of All (1982), turned to Dino De Laurentiis, who agreed to help out if Scheimer could finagle the rights for him to make a theatrical film. Impressed with Scheimer's results and the prospect of cashing in on the theatrical version, NBC shelved the animated movie for a handful of years, had Scheimer's company recut it and turned it into the Saturday morning series Flash Gordon (1979).
According to the book Dino: The Life and Film of Dino De Laurentiis, Sam J. Jones kept getting into fights during the filming of the movie. At one point, Jones was in the hospital with a big scrape on his face, and De Laurentiis himself barged into the operating room to make sure they fixed his face, so as not to leave a visible scar. But Jones kept causing trouble, and then at Christmas, he left for Los Angeles and never returned. So De Laurentiis recalls that he told Mike Hodges, "We'll keep going, with the very best stand-in you can find."
This movie was photographed by veteran British Cinematographer Gilbert Taylor, who had been the Director of Photography on Star Wars: Episode IV - A New Hope (1977). Taylor's distinctive camera work, which has a dreamlike, hazy look, emphasizing the fantasy element (accomplished with the use of filters) is in full effect on this movie.
Lorenzo Semple, Jr. was pressured to make the film funny, even though he says now was "a terrible mistake." He said, "Dino wanted to make Flash Gordon humorous. At the time, I thought that was a possible way to go, but, in hindsight, I realize it was a terrible mistake. We kept fiddling around with the script, trying to decide whether to be funny or realistic. That was a catastrophic thing to do, with so much money involved. I never thought the character of Flash in the script was particularly good. But there was no pressure to make it any better. Dino had a vision of a comic strip character treated in a comic style. That was silly, because Flash Gordon was never intended to be funny. The entire film got way out of control."
A comic book adaptation of the film was drawn by artist Al Williamson, who had previously worked on Flash Gordon comics in the 1960s. Williamson actually disliked the movie, especially the casting of Sam J. Jones, whom Williamson felt did not resemble the classic character.
In the original script, Flash and Dale first meet at a Canadian resort called Dark Harbor. Although they flirt with each other, they don't become acquainted until they're sharing the ill-fated plane ride to New York City. Dale later talks briefly about Dark Harbor during her tear-filled meeting with Flash before his execution.
Klytus and Kala, Ming's two chief henchmen, were competitors for their ruler's favor. Ming played them off against each other to keep them from teaming up against him. This was downplayed in the film to keep the storyline fluid.
Dr. Zarkov's backstory was that he was a N.A.S.A. scientist, who was fired for his paranoid fantasies that Earth was going to be attacked from outer space. Sixty Minutes (1983) derided him as "A Poor Man's Billy Mitchell".
Richard O'Brien found the whole experience of making the film tedious. He did, however, get a lot of pleasure from sitting in the personalized chairs of the principals. His impish behavior wasn't curbed at all. He knew Mike Hodges very well, much to the consternation of the stars, who regularly complained about him on-set.
In the original comic strips, the character known as Kala was the King of the Shark Men (from the undersea kingdom of Mongo), rather than the German-accented female general of Ming's forces played in the movie by Mariangela Melato. Likewise, Prince Thun was the King of the Lion Men of Mongo in the strips (and in the Universal serial), unlike the more human character George Harris plays in the movie.
During the football battle, in the background are a group of bikini-clad women wearing plastic helmets and plastic coats, these are Queen Fria's entourage from the Mongo ice kingdom of Frigia, where it is too cold not to wear the plastic suits.
Nicolas Roeg was originally going to direct, but didn't, due to creative difference. One of his proposals was to excise the trademark cliffhangers and melodrama, seeing Flash as more of "a metaphysical messiah".
At the beginning of the film, as Ming is sending Rays to destroy the Earth. He did not know what the planet he was destroying was called. However one of the buttons on his destruction console said earthquake.
According to to the movie bio book "Easy Riders, Raging Bulls", Star Wars happened because George Lucas really wanted to do a Flash Gordon update. A souped up version with great production values, but he couldn't get the rights to it, so he did he did his own poor man's version of it (which wound up being much more successful than any Flash Gordon version that had come out before it.) Ironically the success of Star Wars led to this 1980 Flash Gordon reboot getting made.
Kurt Russell turned down the role of Flash Gordon because he disliked the slapstick carefree nature of the film and he did Escape from New York (1981) instead. Many years later, Kurt Russell starred as Ego in the MCU film Guardians of the Galaxy: Vol. 2 (2017).
The trivia items below may give away important plot points.
Early in the film, Ming is always shot from below, putting him above the audience. Later, as Flash begins to unite forces, he's shot level with the audience. Towards the end, we start seeing Ming shot from above, symbolizing his defeat.
A scene from Doctor Who: Last of the Time Lords (2007), which a unidentified hand is seen picking up the ring of the Master (John Simm) at his funeral pyre. The Master's evil laugh is heard, mirroring the final scene of this film.
According to Peter Wyngarde, the hand that picks up Ming's ring at the end of the film is Klytus. Despite dying in the film, Klytus gets a new body and becomes the main villain in the sequel that never got made.