!!The novel
* WriteWhatYouKnow: The story was based on Ken Kesey's experiences while working at the Veterans Administration Hospital in Menlo Park, California.
!!The stage adaptation
* AllStarCast: The 1963 Broadway adaptation had Creator/KirkDouglas as [=McMurphy=], Creator/WilliamDaniels as Harding, and a young Creator/GeneWilder as Billy Bibbitt.
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!!The movie
* AbilityOverAppearance: Creator/JackNicholson looks nothing like the character as described in the book but was cast because of his acting ability.
* ActorInspiredElement: Nurse Ratched [[NoFullNameGiven wasn't given a first name]] in the novel. Creator/LouiseFletcher chose "Mildred".
* AllStarCast: Includes Creator/JackNicholson, Creator/LouiseFletcher, Creator/BradDourif, Creator/SydneyLassick, Creator/ChristopherLloyd, Creator/DannyDevito, Creator/VincentSchiavelli, Creator/MichaelBerryman, and Creator/ScatmanCrothers.
* AmateurCast: Will Sampson (Chief Bromden) was a park ranger in Oregon near where the movie was shot, and only landed the part because the casting department couldn't find any other Native American actor who fit the character's physical description. Sampson's appearance in this film led him to a modest acting career in TV and B-movies for the rest of his life.
* CastTheExpert:
** Dr. Spivey was played by Dr. Dean R. Brooks, the real-life superintendent of the Oregon State Hospital who also served as a technical advisor for the film.
** Mel Lambert (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.
* CreativeDifferences:
** Creator/JackNicholson and director Creator/MilosForman had a falling-out over [=McMurphy's=] motivation during pre-production of the film adaptation, leading to the two men to stop speaking to each other, at least for a while.
** Creator/KenKesey grew more and more dissatisfied with the changes Forman was making to his original story and cut ties to the production near the end.
* CreatorBreakdown: Emotionally strained by a demanding shooting schedule that kept him 3,000 miles from his girlfriend (and future wife) Creator/RheaPerlman, Creator/DannyDeVito developed the coping mechanism of an ImaginaryFriend with whom he would have nightly chats. Concerned that his own sanity might be slipping away, [=DeVito=] sought the advice of Dr. Brooks, who assured him that there was no reason to worry as long as [=DeVito=] could still identify the character as fictional.
* DemotedToExtra: One of the reasons why Dale Harding, a major character of the novel, is only given a handful of lines in the film is that William Redfield, the actor playing Harding, was dying of leukemia and was severely ill throughout the filming. Several scenes were written that gave him a more prominent role, but they were never filmed because Redfield barely had the strength and health to perform in the few scenes that he had.
* DevelopmentHell: After starring as [=McMurphy=] in a 1963 Broadway adaptation of the novel, Creator/KirkDouglas obtained the movie rights and spent a decade trying to obtain funding. By the time that his son, Creator/MichaelDouglas, was finally able to secure a production deal, Kirk had gotten too old (and/or unbankable) for the role.
* DisabledCharacterDisabledActor: ''Actual patients'' from the institution where the film was shot were used as extras.
* DisownedAdaptation: The only time Creator/KenKesey ever watched any of the movie was when he was channel-surfing one night and randomly came across it. He changed the channel once he realized what it was. He even sued the movie's producers because it wasn't shown from Chief Bromden's perspective (as the novel is).
* EnforcedMethodActing:
** The script called for [=McMurphy=] to leap on a guard and kiss him when first arriving at the hospital. During filming, Creator/MilosForman decided that the guard's reaction wasn't strong enough, and told Creator/JackNicholson 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.
** Forman would roll the cameras when the cast members didn't know it, so he could capture the "real moment".
* HypotheticalCasting: Ken Kesey wanted Creator/GeneHackman to play [=McMurphy=] in the film, while Milos Foreman wanted Creator/JamesCaan.
* MethodActing: Many of the cast members stayed in character, even when the cameras weren't rolling.
* OneTakeWonder: The final scene was shot in one take, whereas the party scene took four nights.
* PlayingAgainstType:
** Billy would definitely be one if Creator/BradDourif's career playing various creepy, evil characters had already been established.
** Those who know Creator/DannyDeVito primarily for such sleazy, jerkass roles as [[Series/{{Taxi}} Louie DePalma]] and [[Series/ItsAlwaysSunnyInPhiladelphia Frank Reynolds]] will be surprised by his portrayal of the gentle, ever-smiling Martini.
* RoleReprise: A then-little-known Creator/DannyDeVito was the only actor to keep his role from the stage version.
* ScullyBox: When [=McMurphy=] first meets the Chief, the Chief must be standing on a lifting box. You can't see his feet in the shot. Creator/JackNicholson is 5' 10". Will Sampson was 6' 7". In the shot, Nicholson's shoulders appear only to come up to Sampson's elbows. Also, the finished height of most doorways is 6' 8" and Sampson's head appears to extend higher than that in the shot. Even accounting for perspective, he might be on a 5" plus box. Nowhere else in the movie is the height difference so apparent.
* ThrowItIn:
** The Indian war dance wasn't in the script. It was Creator/JackNicholson's idea.
** According to Josip Elic, Nicholson improvised the scene where he gets on Brancini's shoulders to play basketball. Nicholson told him, "If I fall, I close this picture down for a week." Elic replied, "If I fall, I close this picture down for two weeks."
* WhatCouldHaveBeen:
** Creator/KirkDouglas, who'd played [=McMurphy=] in the 1963 play and bought the movie rights, planned to star himself, but by the time they got around to making the film he was too old.
** Creator/MarlonBrando, Creator/PeterFonda, Creator/{{Steve McQueen|Actor}}, Creator/BurtReynolds, and Creator/JonVoight were considered for [=McMurphy=] before Creator/JackNicholson was selected.
** Creator/AnneBancroft, Creator/EllenBurstyn, Creator/FayeDunaway, Creator/JaneFonda, Creator/AudreyHepburn, Creator/AngelaLansbury, Creator/JeanneMoreau, and Creator/ShirleyMacLaine were all offered the role of Nurse Ratched. Creator/LilyTomlin was actually cast in the part but subsequently backed out in order to appear in Creator/RobertAltman's ''Film/{{Nashville}}'' (in a role that had originally been intended for Creator/LouiseFletcher).
** Creator/BudCort was originally considered for Billy Bibbit.
** Creator/RobertForster was considered for the role of Martini.
** Creator/MilosForman had considered Creator/ShelleyDuvall for the role of Candy. While screening ''Film/ThievesLikeUs'' to see if she was right for the role, he became interested in Creator/LouiseFletcher, who had a supporting role, and decided to cast her as Nurse Ratched. Duvall later enquired about playing the role of Rose, but was turned down; had she been accepted, this movie would have had all three members of the principal adult cast of ''Film/TheShining'' on board, five years before that film's release (the other two being Nicholson and Creator/ScatmanCrothers, who played Turkle).
** Creator/WernerHerzog was asked to direct. Creator/HalAshby was also considered to direct, though he did recommend that Nicholson play [=McMurphy=].
** Having played an orderly in the stage production, Creator/MichaelDouglas originally wanted to play Billy Bibbit in the film. Creator/RandyQuaid was considered for the aforementioned role.
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