Jack Nicholson and Louise Fletcher’s iconic, Oscar-winning performances as McMurphy and Nurse Ratched in One Flew Over the Cuckoo’s Nest are forty years old today.

The hit movie, based on Ken Kesey’s classic novel about a rebel in a mental institution who rallies his fellow patients to stand up to their iron-fisted head nurse, held its world premiere on 19 November 1975.

Decades and multiple award wins later, One Flew Over the Cuckoo’s Nest still stands as one of the greats, but there is a lot fans might not know about their favourite anti-establishment film. What better time to learn more?

It swept all five of the top Academy Awards

That’s a win for Best Picture, Best Director, Best Actor, Best Actress and Best Adapted Screenplay. Only It Happened One Night from 1935 and The Silence of the Lambs in 1991 have also accomplished this ‘top five’ feat. So, a good night, then.

Actors who played patients lived on a psychiatric ward during shooting

That’s right, all cast members playing patients stayed in Oregon State Hospital’s psychiatric centre, meaning they regularly spoke with real life patients and truly ‘lived’ the movie, even personalising their sleeping areas. Talk about method acting.

Jack Nicholson inspires his fellow patients to rise up against oppression (IMDB)

The soundtrack is possibly the most bizarre ever

Take some wine glasses, stroke them, and mix a bowed saw with some guitar. That’s the sound rock producer Jack Nitzsche went for, so no wonder you quickly end up questioning your own sanity when listening to it.

Kesey didn’t want Jack Nicholson cast and has never seen the film

In Kesey’s book, Chief Bromden is the narrator, and he was unhappy that this would be not be translated to the big screen. He claims never to have watched the movie, despite its huge success

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Other actors were considered for McMurphy first

Director Milos Forman originally contacted Burt Reynolds, Marlon Brando and Gene Hackman for the lead. Kirk Douglas had longed to play the role but was too old at the time.

Nicholson refused to speak to Forman for much of shooting

Nicholson was angered when Forman suggested that the hospital patients should be unruly when McMurphy arrives, insisting that they should only start rebelling after his character impacts upon their lives. Nicholson reportedly did not speak to Forman during much of the shooting because of their artistic differences. Rumours has it the cinematographer was forced to play middle man when they needed to communicate.

Chief Bromden's casting is a story in itself

Will Sampson, who plays Chief, was chosen for the part because he was the only Native American the casting team could find who matched the character’s huge size. Measuring 6”5, he was employed as a park range in Oregon near where the movie was being filmed.

Will Sampson finally coming into his own as Chief Bromden (IMDB)

20th Century Fox wanted to change the ending

Fox was interested in distributing the film but only if the closing scenes were rewritten to let McMurphy live. Producers refused and United Artists won the movie.

Psychiatric nurses played extras

Those people you don’t recognise in the background of shots were played by actual employees of the Oregon State Hospital’s psychiatric centre. Facility superintendent Dr Dean Brooks was cast as Dr John Spivey, who assesses McMurphy’s mental health. Just another day in the office.

Ken Kesey did not want Jack Nicholson to play McMurphy (IMDB)

Danny DeVito sought psychiatric help during filming

DeVito was 3,000 miles away from his girlfriend Rhea Perlman and to cope with the separation, he invented an imaginary friend to talk to at night. He became concerned about his mental health and sought Dr Brooks’ advice, who told him that he should not be worried so long as he was still aware that that character was made-up.

But Sydney Lassick sparked real concerns

Dr Brooks became worried about the psychological state of Lassick, who played Charlie Cheswick. He began displaying erratic behaviour while in character and eventually had to be removed from set after bursting into tears watching the final scene between McMurphy and Chief.

Jack Nicholson and Chief Bromden in the closing scene (IMDB)

Forman often filmed the actors without them knowing

He led unscripted therapy sessions and shot plenty of footage of the actors out of character. One shot of Fletched reacting coldly to a piece of direction was included in the final edit.

Fletcher once stripped off to try and bond with her co-stars

Fletcher randomly ripped off her dress on the ward one evening, much to the surprise of her castmates, after becoming envious of their friendship. She wanted to show them that she was a “not a cold-hearted monster” and actually nothing like her character Ratched.

Louise Fletcher as the authoritarian Nurse Ratched (IMDB)

Kesey was inspired to write the book after working a night shift in an asylum

He had also been taking part in government-backed experiments with psychoactive drugs, which explains why the creativity flowed freely, even when the storyline focused on oppression.

‘One Flew OUT of the Cuckoo’s Nest’

A crew member accidentally left a second story window open at the hospital and a real patient climbed through the bars and fell out, hurting himself. The Statesman Journal picked up on the accident and ran a story with the headline reading “One flew OUT of the Cuckoo’s Nest”.