At one point an amusing exchange occurs:
Coppola: Now, the early Star Wars script you showed me, how was that different?
Lucas: Well, the twins were there and Vader was the father...
Coppola: Really? They were there--
Lucas: There were there [goes on to talk about other stuff]
Or something close to that. I have no idea where it is from or what the actual quote is but I've been dying to find out. Does anyone here know about this?