Louise Fletcher was signed a week before filming began, after auditioning repeatedly over six months; director Milos Forman had told her each time that she just wasn't approaching the part correctly, but kept calling her back.
The cast and crew had to become accustomed to working with extras and supporting crew members who were inmates at the Oregon State Mental Hospital; each member of the professional cast and crew inevitably worked closely with at least two or three mental patients.
Most of Jack Nicholson's scene with Dean R. Brooks upon arriving at the hospital was improvised - including his slamming a stapler, asking about a fishing photo, and discussing his rape conviction; Brooks's reactions were authentic.
Mel Lambert, who played the harbor master, was a local businessman rather than an actor; he had a strong relationship with Native Americans throughout the area, and it was he who suggested Will Sampson for the role of Chief Bromden.
Director Milos Forman relied heavily on reaction shots to pull more characters into scenes. In some group therapy scenes, there were ten minutes of Jack Nicholson's reactions filmed even if he had very little dialogue. The shot of Louise Fletcher looking icily at Nicholson after he returns from shock therapy was actually her irritated reaction to a piece of direction from Forman.
The script called for McMurphy to leap on a guard and kiss him when first arriving at the hospital. During filming, director Milos Forman decided that the guard's reaction wasn't strong enough and told Jack Nicholson to jump on the other guard instead. This surprised the actor playing the second guard greatly, and in some versions he can be seen punching Nicholson.
This was the second film to win the grand slam of the Oscars: Best Picture, Best Director (Milos Forman), Best Adapted Screenplay, Best Actor and Best Actress. The first was It Happened One Night, four decades earlier.
Author Ken Kesey was so bitter about the way the filmmakers were "butchering" his story that he vowed never to watch the completed film and even sued the movie's producers because it wasn't shown from Chief Bromden's perspective (as the novel is). Years later, he claimed to be lying in bed flipping through TV channels when he settled onto a late-night movie that looked sort of interesting, only to realize after a few minutes that it was this film. He then changed channels.
During filming, a crew member running cables left a second story window open at the Oregon State Mental Hospital and an actual patient climbed through the bars and fell to the ground, injuring himself. The next day The Statesman Journal in Salem, Oregon reported the incident with the headline on the front page "One flew OUT of the cuckoo's nest".
Rumors that production shut down because Jack Nicholson had hair plugs implanted are false (this can be verified by actually looking at his scalp). The story, as related by production designer Paul Sylbert, was that Nicholson and director Milos Forman had very different ideas about how the narrative should play out; for example, Forman thought that the ward should be in bedlam when McMurphy showed up and Nicholson posited that his character would have absolutely no effect on the mental patients if they were already riled up, which would have negated the purpose of his character and therefore much of the plot. Nicholson and Forman both refused to give an inch, each believing he was right and the other was wrong. The "two months" that Nicholson was supposed to have disappeared was actually closer to two weeks, and he didn't "disappear". In actuality, Nicholson spearheaded a coup among the other actors and refused to let Forman run rehearsals, running them himself instead. During production, Nicholson and Forman spoke to each other through the cinematographer, but faked a friendly relationship when the media and studio personnel would show up to the set. This is one explanation why Nicholson doesn't appear on any of the DVD special features.
Louise Fletcher was so upset with the fact that the other actors could laugh and be happy while she had to be so cold and heartless that near the end of production she removed her dress and stood in only her panties to prove to the actors she was not "a cold-hearted monster".
Will Sampson, who plays Chief Bromden, was a park ranger in Oregon in a park near where the movie was filmed. He was selected for the part because he was the only Native American the Casting Department could find who matched the character's incredible size.
Kirk Douglas starred in the 1963 Broadway production after buying the film rights prior to publication; he later passed the film rights to his son Michael Douglas, but kept a percentage of the profits. Every major studio had declined to make the film during the period he was trying to star in it. Kirk had met Milos Forman in Prague while on a State Department tour and promised to send him the book after deciding he would be a good director for the film; the book never arrived, probably confiscated by censors of the Czech government, which was Communist at the time. Ken Kesey wrote a screenplay for the production, but Forman rejected it because Kesey insisted on keeping Chief Bromden's first-person narration.
During the ECT scene, McMurphy says "A little dab will do ya" as the nurse is putting conductor gel on the side of his head. This phrase, not in the original script, is a reference to the advertising jingle of Brylcreem hair cream, which was a popular hair care product for men in the 1960s and 1970s.
Neither the film nor Ken Kesey's 1962 novel made specific reference to Oregon State Hospital. Kesey was inspired by his experiences working at a veterans' hospital in California, and set his novel at an unnamed institution in Oregon.
A portion of the original NBC Radio broadcast of Game 2 of the 1963 World Series was used for the scene where the orderlies are listening to the game on the radio. Hall of Fame baseball announcer Ernie Harwell can be heard on the broadcast.
The play opened on Broadway in New York City, New York, USA on 13 November 1963 and closed on 25 January 1964 after 82 performances. The opening night cast included Kirk Douglas as R.P. McMurphy, William Daniels as Dale Harding and Gene Wilder as Billy Bibbit.
To call Ken Kesey's time at the VA hospital in Palo Alto is misleading. While a graduate student in Creative Writing at Stanford, he volunteered for experiments on the effects of LSD - which gave rise to the many surreal parts of the novel (deleted, along with the narrator's role, by Milos Forman). Kesey's experience with LSD led to the legendary bus trips, the Trips Festival, and all the events chronicled in Tom Wolfe's 'The Electric Kool-Aid Acid Test'.
When Louise Fletcher neared the end of her Best Actress Oscar acceptance speech, she finished with a unique touch (a first in American Sign Language): "For my mother and my father, I want to say thank you for teaching me to have a dream. You are seeing my dream come true. Thank you."
Milos Forman said he directed the movie in a naturalistic style significantly contrasting with the "totally stupid socialist rallies and movies" which were common in his native Czechoslovakia. "I was fascinated just to see real faces on the screen," he said. "That's what cinema verite [like Titicut Follies] taught me."
Accepting the Best Picture award, producer Michael Douglas said that "Cuckoo's Nest" was the first picture since It Happened One Night to receive the four major Oscars: Best Picture, Best Director, Best Actor, and Best Actress. However, Douglas incorrectly stated the Capra classic's year of release as 1937, not 1934.
Jack Nicholson, Danny DeVito and Vincent Schiavelli play the inmates of an asylum. All three ended up as villains in Tim Burton's Batman films: Nicholson was the Joker in Batman, DeVito and Schiavelli were the Penguin and the Organ Grinder respectively in Batman Returns.