While retaining many of the novel's themes and motifs, the filmed version of One Flew Over the Cuckoo's Nest differs in several significant ways. The film, released in 1975, won Academy Awards for Best Picture, Best Actor (Jack Nicholson), Best Actress (Louise Fletcher), Best Screenplay Adapted from Other Material (Lawrence Hauben and Bo Goldman), and Best Director (Milos Forman). Since its release, the film has been certified as one of the Top 100 American Films by the American Film Institute.
The film is also noted for its casting, which includes early cinematic appearances by such later respected actors as Brad Dourif (Billy Bibbit), Christopher Lloyd (Taber), and Danny DeVito (Martini). Other actors include real hospital superintendent Dr. Dean Brooks (Doctor Spivey), Will Sampson (Chief Bromden), Sydney Lassick (Charlie Cheswick), Marya Small (Candy Starr), and William Redfield (Dale Harding).
The most notable difference between the film and the novel is the story's point of view. In the novel, Chief Bromden is the narrator who reveals the story of the battle of wills between Nurse Ratched and Randle Patrick McMurphy. In fact, Chief arguably is the novel's hero who undergoes the most notable changes in the novel. While detailing the events in the mental institution, Chief reveals biographical information of his own life before his institutionalization. We learn that Chief is a paranoid schizophrenic, a war veteran, and a half-breed Indian whose white mother conspired with the U.S. government to emasculate his proud father, an American Indian whose name Tee Ah Millatoona translates as "Pine-That-Stands-Tallest-on-the-Mountain."
The filmed version discards Chief as the story's narrator, discards the background story of Chief, and relegates his character to a secondary — albeit important — character to McMurphy. In the film, McMurphy is clearly the hero.
Chief's delusional episodes of witnessing the inner workings of the Combine and its fog machines are eliminated in the film in favor of scenes written that omnisciently expand on McMurphy's character and his background, as well as expand on his charitable nature.
In addition, Chief eventually becomes fully communicative in the novel while muttering only one phrase — "Juicy Fruit" — in the film. This explains how McMurphy is able to bring Chief along on the fishing excursion in the novel, a detail not explained in the film.
The film also softens McMurphy's more objectionable behavior in the book. Instead, he becomes more of a roguish con man than an unpredictably fearsome individual prone to bursts of physical violence against others to achieve his ends. Also missing from the film are several key symbolic elements, including McMurphy's poker-hand tattoo that foreshadows his death. The tattoo depicts aces and eights, known as the dead-man's hand in accordance to the legend of the poker hand held by Wild Bill Hickock when he was murdered.
In the film, McMurphy boasts that he was conned into statutory rape by a teenaged girl who lied about her age. "But Doc, she was fifteen years old, going on thirty-five, Doc, and, uh, she told me she was eighteen and she was, uh, very willing, you know what I mean," Nicholson's McMurphy asserts. "I practically had to take to sewin' my pants shut. But, uh between you and me, uh, she might have been fifteen, but when you get that little red beaver right up there in front of ya, I don't think it's crazy at all now and I don't think you do either. No man alive could resist that, and that's why I got into jail to begin with. And now they're telling me I'm crazy over here because I don't sit there like a goddamn vegetable. Don't make a bit of sense to me. If that's what's bein' crazy is, then I'm senseless, out of it, gone-down-the-road, wacko. But no more, no less, that's it."
In the novel, McMurphy's boasts of being seduced by a nine-year-old girl are related with a sense of false bravado and world-weariness. His initial incarceration isn't for statutory rape, it's for being "a guy who fights too much and fucks too much." In the novel, McMurphy freely admits to conning his fellow patients for his own financial gain. The film only shows McMurphy winning cigarettes from his comrades.
Certain critical scenes from the novel are eliminated in the cinematic version. Of these, the suicide of Cheswick, is most notable. Cheswick's character was the first individual in the novel to receive invigoration from McMurphy's antics. When McMurphy decides to toe the line — that is, conform to Nurse Ratched's wishes — it is after hearing from the swimming pool lifeguard that the length of their mutual confinements is entirely at the discretion of Nurse Ratched. It is in the same pool that Cheswick — feeling abandoned and betrayed by McMurphy's subsequent conformist behavior — chooses to drown himself.
One scene not in the film is McMurphy's final con against the Acutes. In the novel, McMurphy manipulates Chief Bromden to lift the control panel after McMurphy takes bets from the Acutes that it can't be done. McMurphy, of course, had already hedged his bet by having Chief display his ability to lift the panel previously. When Chief performs the trick for the Acutes, he feels used and betrayed by McMurphy. The film balances a scene of McMurphy unsuccessfully trying to lift a basin with the scene of Chief lifting it successfully and flinging it through the window while avoiding the scene of Chief lifting it to win a bet for McMurphy.
Another sequence in the film differs greatly from the novel. The fishing episode in the novel is a planned event that Nurse Ratched repeatedly attempts to sabotage. Despite this, McMurphy convinces Doctor Spivey to join the group when the alluring prostitute Candy arrives with only one car. In the filmed version, McMurphy hijacks a waiting institutional bus and instructs the film's principal male cast to participate in an act of rebellion. As a result, the scene at the gas station, when McMurphy confronts the surly and abusive attendants, temporarily empowers the patients, and Doctor Spivey is not depicted. Additionally missing is the scene when the group passively endures the jeers and taunts of the fishermen at the dock.
In the film, McMurphy's character remains the same roguish noncomformist up until his lobotomy. The book, however, details Chief's observations of McMurphy's short-lived attempt to conform to Nurse Ratched's rules and the other patients' distrust of McMurphy engendered by Nurse Ratched, as well as McMurphy's increasing sadness and sensing of his own withering strength and impending doom.
The film also differs from the novel in its depiction of the events leading to McMurphy's introduction to electroshock therapy. The novel carefully establishes a character not in the film, Big George. George's obsession with cleanliness is established prior to the fishing excursion, and becomes a pivotal plot element when Nurse Ratched orders the African-American orderly, Washington, to administer an enema to George in the shower. Washington's threatening behavior toward George prompts McMurphy to reluctantly challenge the orderly. The resulting melee is the impetus for Nurse Ratched to send McMurphy and his accomplice, Chief Bromden, to the Disturbed Ward, where they receive electroshock therapy. The film employs the initial altercation between McMurphy and Washington as the impetus for Nurse Ratched to send McMurphy, Chief, and Charlie Cheswick (who doesn't commit suicide in the film) to the Disturbed Ward.
Perhaps the most telling difference between the film and the novel is the ending. The novel contains an episode missing from the film wherein Chief observes a dog sniffing gopher holes from the hospital window. The dog is distracted by a flock of geese forming a cross against a full moon. The dog chases the geese toward a road where it is implied the dog will confront an automobile with the inevitably tragic result that machine will triumph over nature. Coincidentally, this is the same course the Chief follows when he escapes from the hospital, giving the novel's resolution a degree of uncertainty as to whether the Chief will succeed in the outside world or succumb to a worse fate in a world increasingly overrun by dehumanizing mechanization. The film's conclusion, however, depicts Chief running from the hospital toward what the viewer assumes is happiness and liberty.
Exhibiting pronounced differences from the novel, the film nonetheless retains the themes of natural versus institutional, the battle of creative nonconformity against arbitrary and autocratic authority, the redemptive qualities of unrepressed sexuality, and the desultory effects of unbalanced feminine dominance.
While the film is generally regarded a cinematic masterpiece, Ken Kesey has vowed he will never view it due to disputes with the film's producers, Michael Douglas and Saul Zaentz. Douglas's father, the actor Kirk Douglas, was the first actor to portray McMurphy in the 1960s stage version of the novel. Former Creedence Clearwater Revival singer-songwriter John Fogerty's perception of Zaentz's business practices, coincidentally, were the subject of a disparaging song and video entitled "Zaentz Can't Dance."