Mike Nichols originally asked Bob Balaban to read for the role of Milo Mindbender, ultimately played by Jon Voight. However, after hearing him, he changed his mind and thought Balaban perfect for Captain Orr.
Stacy Keach was initially cast as Colonel Cathcart; Mike Nichols did not like the job he did and replaced him with Charles Grodin (who had been cast as Aarfy Aardvark) in makeup. Grodin was himself eventually replaced by Martin Balsam and moved back into the role of Aarfy.
Creator-Preferred Adaptation: Despite the changes in the screenplay, Joseph Heller approved of the film, according to the DVD Commentary by Mike Nichols and Steven Soderbergh. According to Nichols, Heller was particularly impressed with a few scenes and bits of dialogue Buck Henry created for the film, and said he wished he could have included them in the novel.
Fatal Method Acting: Second Unit Director John Jordan refused to wear a harness during a bomber scene. While giving a hand signal to another airplane from the tail gunner position in the camera plane, he lost his grip and fell four thousand feet to his death.
Throw It In!: Since most of the location filming took place on a small airfield in rural Mexico the entire production was set up like a military encampment including uniforms so they could film in any direction at any time without worrying too much about who or what showed up in the background. The men conducting maintenance and flight operations in the background really are conducting flight operations in the background. Why bother hiring a bunch extras to portray men servicing aircraft when you can just film the mechanics actually doing it?
Gene Wilder was the original choice for Milo Minderbender and he was eager to take the role until he saw the screenplay and disagreed with the creative direction of the character. Jack Lemmon was also considered.
In addition to Art Garfunkel, Paul Simon was originally going to be in the film, but his role was written out.
About the series:
Cast the Runner-Up: Executive producer/director George Clooney was originally to play the role of Colonel Cathcart, but decided to take the smaller role of Scheisskopf and cast Kyle Chandler as Cathcart instead, making the miniseries the second adaptation where Cathcart was recast.
Descended Creator: George Clooney is an executive producer on the series and directed two of the episodes. He also plays Scheisskopf.