The 14-year-old son of Robert Altman, Mike Altman, wrote the lyrics to the theme song "Suicide is Painless". Because of its inclusion in the subsequent TV series, he continued to get residuals throughout its run and syndication. His father was paid $75,000 for directing but his son eventually made about $2,000,000 in song royalties.
Robert Altman says that during filming, Elliott Gould and Donald Sutherland together went to the studio and complained that Altman was filming too much of the secondary characters. They requested that he be removed from the film, but the studio refused. After the film was completed and received its accolades, only Gould confessed the matter to Altman. As a result, he received parts in other Altman pictures, whereas the director never again used Sutherland.
The first take of the shot where Hot Lips is revealed in the shower didn't work because Sally Kellerman anticipated the reveal and was already lying on the floor when the tent flap went up. To distract her, Robert Altman and Gary Burghoff entered the shower tent and dropped their trousers while the shot was rolling outside. While Kellerman was staring at them, the tent flap was raised, resulting in her genuine surprise and shock when she realized what had happened. In the special double disc dvd they say that Radar is standing naked beside the camera and that that's the reason why Sally Kellerman looks so surprised when the flap was raised.
The story goes that Robert Altman was editing the movie with his editor, Danford B. Greene; they had nude pinups on the walls of the editing room. The head of postproduction came by and tried to stop Altman from using the editing machine, as he wasn't a designated editor, and Altman threw him out of the editing room. The next day a memo came down from the Fox front office, stating a new policy that there were to be no pinups on the walls of editing rooms. Altman took the memo to the sound recording studio and added it as one of the loudspeaker announcements during the film.
In the opening titles, when a soldier carrying a wounded soldier on a stretcher and when the soldier trips and falls down, it wasn't scripted. It was actually an accident by the actor who tripped over something. Robert Altman decided that instead of editing it out, to use it to foreshadow the dark humor theme as the movie's first small, but real, laugh.
When studio execs first saw the dailies, they complained to Robert Altman that the soldiers looked dirty compared to the soldiers in Tora! Tora! Tora! (1970) and Patton (1970). Altman, a veteran of WWII, replied that soldiers in war are dirty. The next day the execs told the producers of those two films to make their soldiers look dirtier.
According to Elliott Gould, Sylvester Stallone revealed to him that he was an extra in this film. When Gould later told this to Robert Altman, Altman refused to accept this as fact because he was not a fan of Stallone's work.
Tom Skerritt recalled that the dialogue was about 80% improvised. In order to create a different kind of atmosphere, Altman cast some of the parts from improvizational clubs who had no previous movie experience.
The operating scenes were almost cut out due to their graphic nature. However, two women who were visiting the set told the producers that the operating scenes were what made the movie, and should be kept in.
One innovation of Robert Altman was the almost constant overlaying of dialogue: as many as four conversations could be happening at once in a given shot. While this was considered unorthodox and revolutionary at the time, Altman's instinct was vindicated when audiences agreed that the technique contributed to the feeling that war was "messy and confusing". The technique has been emulated on several occasions since.
The opening title sequence has a text that identifies the place as Korea. This was added at the insistence of the studio after director Robert Altman had removed every reference to Korea, intending it to be mistaken for Vietnam, which would reinforce the anti-war statement.
Writer Ring Lardner Jr. was the only Academy Award winner out of the movie's five nominations. Lardner practically disowned the movie when he saw that very little of his original script made it into the final cut.
The scene where Father Mulcahy is blessing the jeep was improvised. Actor Rene Auberjonois found the blessing in a copy of the Army Chaplain's Handbook, and thought it would be a good addition to both the story and to his character. The director agreed, and the scene was shot in one take.
Robert Altman felt that he was able to get away with so much during shooting because the officials at 20th Century Fox were keeping a closer watch on their two massively expensive projects, also war films, Patton (1970) and Tora! Tora! Tora! (1970).
When the movie was released, the military wanted not to run the movie in their theaters because of its anti-war message. The case went to the Supreme Court which ruled the military could not withdraw the film for this reason. Instead, the military chose to run Patton (1970) in the following week feeling that film was more complimentary to the military.
The loudspeaker shots and announcements were added after the editing process had begun and the filmmakers realized that they needed more transitions. Some of the loudspeaker shots have the Moon visible and were shot while the Apollo 11 astronauts were on the Moon.
This and Catch-22 (1970), two films satirizing recent American wars, were released in the same year. "Catch-22," based on a best-selling novel, featuring a huge cast, and boasting director Mike Nichols fresh from his success with The Graduate (1967), was expected to be the more successful film. When the reverse proved true, Robert Altman hung a banner in his office reading, "Caught-22."
Robert Altman was originally promised five "points" (a percentage) of the film's profits. After a disagreement between Altman and one of the Fox executives, the offer of points was taken back before production began. When the film became a big hit, Altman's agent asked for the points back; the studio was considering it when Altman was quoted in the press saying how much he hated working for Fox. He was never given the points back.
This was not the first Korean War-based movie to carry the title "MASH." In 1953, Humphrey Bogart starred in a film also about a MASH unit by the same title. But the studio thought the title might make audiences think it was about potatoes, so the title was changed to Battle Circus (1953).
During filming Donald Sutherland and Elliott Gould became so frustrated with the directorial style of Robert Altman (who often had his actors talk over each other at the same time, to simulate real life conversation), that they went to the head of production to demand he be fired. They were concerned that the movie would end up as a mess, and a movie disaster at the box office might ruin their careers. They were told by the studio head not to worry, that the movie would only be seen at a few drive-ins across the country, and that hardly anyone would ever see the movie.
This film was among the first to be released on home video. In 1977 20th Century Fox licensed 50 of its titles to a fledgling video duplication company called Magnetic Video Corp. Fox purchased the company in 1978, laying the groundwork for its current successful video operation.