Wow. In 1978, George Lucus gathered together Steven Spielberg and screenwriter Lawrence Kasdan to go over ideas for a film Lucas had wanted to make about a swashbuckling archeologist, i.e. Raiders of the Lost Ark. Their sessions were recorded and there's a transcript available online.
Lucas - Now, several aspects that we've discussed before: The image of him which is the strongest image is the "Treasure Of Sierra Madre" outfit, which is the khaki pants, he's got the leather jacket, that sort of felt hat, and the pistol and holster with a World War One sort of flap over it. He's going into the jungle carrying his gun. The other thing we've added to him, which may be fun, is a bull whip. That's really his trade mark. That's really what he's good at. He has a pistol, and he's probably very good at that, but at the same time he happens to be very good with a bull whip. It's really more of a hobby than anything else. Maybe he came from Montana, someplace, and he... There are freaks who love bull whips. They just do it all the time. It's a device that hasn't been used in a long time.
Spielberg - You can knock somebody's belt off and the guys pants fall down.
Lucas - You can swing over things, you can...there are so many things you can do with it. I thought he carried it rolled up. It's like a Samurai sword. He carries it back there and you don't even notice it. That way it's not in the way or anything. It's just there whenever he wants it.
Spielberg - At some point in the movie he must use it to get a girl back who's walking out of the room. Wrap her up and she twirls as he pulls her back. She spins into his arms. You have to use it for more things than just saving himself.
Lucas - We'll have to work that part out. In a way it's important that it be a dangerous weapon. It looks sort of like a snake that's coiled up behind him, and any time it strikes it's a real threat.
Kasdan - Except there has to be that moment when he's alone with a can of beer and he just whips it to him.
Patrick Radden Keefe at the New Yorker read through the whole thing and has some highlights and general thoughts.
Over the intervening decades of enormous wealth and success, both Lucas and Spielberg have carefully tended their public images, so there is a voyeuristic thrill to seeing them converse in so unguarded a manner. As the screenwriters Craig Mazin and John August pointed out recently on the Scriptnotes podcast, one delight of reading the transcript is watching Spielberg throw out bad ideas, and then noting how Lucas gently shuts him down. Spielberg, who had sought to direct a Bond movie-and, astonishingly, been rejected-thought that their hero should be an avid gambler. Lucas replied that perhaps they shouldn't overload him with attributes. (Lucas himself had briefly entertained, then mercifully set aside, the notion that his archaeologist might also be a practitioner of kung fu.) There's a good reason we seldom get to spy on these conversations: really good spitballing, like improv comedy, requires a high degree of social disinhibition. So the writers' room, like a therapist's office, must remain inviolable.