 Rumors that production shut down because Jack Nicholson had hair  plugs implanted are false (this can be verified by actually looking  at his scalp). The story, as related by production designer Paul  Sylbert, was that Nicholson and director Milos Forman had very  different ideas about how the narrative should play out; for  example, Forman thought that the ward should be in bedlam when  McMurphy showed up and Nicholson posited that his character would  have absolutely no effect on the mental patients if they were  already riled up, which would have negated the purpose of his  character and therefore much of the plot. Nicholson and Forman both  refused to give an inch, both believing they were right and the  other was wrong. The two months that Jack Nicholson disappeared for  was more like two weeks, and he didnt disappear. In actuality,  Nicholson spearheaded a coup among the other actors and refused to  let Forman run rehearsals, running them himself instead. During  production, Nicholson and Forman spoke to each other through the  cinematographer, but faked a friendly relationship when the media  and studio personnel would show up to the set. This is one  explanation for why Nicholson doesnt appear on any of the DVD  special features.