Psycho Censors

Psycho is a genre-defining movie, regarded as one of the finest psychological horror films of all time. The film broke new ground in several ways.
It was also the first film to show a toilet flushing on screen. The censors objected to it and tried have the toilet scene removed, but Hitchcock objected. They eventually gave up trying to fix the film and let the toilet flush be shown. Interesting that the offending flush takes place about forty seconds before a character is brutally stabbed to death in a shower while completely naked.

Incidentally, Alfred Hitchcock staged the shower murder scene in such a way the censors could not find a specific shot that broke the censor's rules.