This is what Warren Beatty said about working with Diane in "Reds" at a press-conference because of the dvd launching:

"There is, of course, a yarn connected with each person," Beatty said. "There's pretty much nobody in the movie who didn't fascinate me. Diane Keaton. You know, some people say that casting is character when you're making a movie. When you're close-up on a person, that's who they are. And then there's an old shibboleth that character is plot. I would say to you that Diane Keaton is a plot. And a very interesting plot -- a plot that can go in any direction at any moment. She's filled with comedic response and also a dark response. She can go light and dark, and I always felt that Diane and her subtleties and her sense of humor and her beauty and her intensity pretty much held the story together, because the story is a story that holds the politics and the dialectics of the thing together in the romance between a man and a woman."