Many of the extras seen in the background of One Flew Over the Cuckoo's Nest were actual mental patients

The film was shot almost entirely on location at a working institution in Oregon and the actors spent time with actual patients before filming and patients also served as extras on the set so there is a definite air of authenticity to the film.  To round up a number of particularly ...
Many of the extras seen in the background of One Flew Over the Cuckoo's Nest were actual mental patients