Chief Bromden isn't really crazy, he's having psychic visions of one or more parallel universes that have been conquered by The Combine.Obvious, really.
Bromden's first name is TaylorHe was brought in because the orderlies thought he was delusional for seeing ghosts. He was in before Ratched and the New Orderlies came and pulled on the deaf-mute act for them. He later escaped and took refuge in Canada, before Tangina called for him.
McMurphy isn't really dead, He's Just Hiding.The ending was all one final Batman Gambit so he could get Bromden to lift the sink and break the two out. Because he sees that Chief is the only one strong enough to lift the sink. The final shot wasn't Bromden running in the woods but Mc Murphy, following him.