The cast of One Flew Over the Cuckoo’s Nest
Jack Nicholson, together with the entire cast of One Flew Over the Cuckoo’s Nest, spent a period of time living in the psychiatric hospital where the movie was later filmed. They operated as actual patients and participated in therapy sessions.
The time spent at the mental asylum affected the actors more than they had expected, as Danny DeVito made an imaginary friend during this time, and Sydney Lassick suffered a mental breakdown during the filming.