There is a montage scene of art buyers that is pretty much ad lib.  I just gave the actors suggestions and directions and they had fun.  Those scenes are really funny! 

There is only one scene I can think of where I made stuff up.  Robert Miano started his career as a singer, he told me, so I wrote a couple lines into the film where Robert asks Louise Post (Veruca Salt) what she does and she says she's a singer.  Robert has a big grin in that scene.  I thought it would be cool for him, so I added the lines.  But these were written before shooting as well.

He's a pretty bad guy. He wears a nice hat, thanks to our Costumer. I think Don liked the hat so much he even kept it. The screenplay was originally 50 pages or so longer and I developed Don's character a lot more and explained why he was so mean. But the basic gist of it was that he had a troubled childhood and he couldn't make it as an artist himself. His parents pushed him to paint and he was never any good at it.

More than being greedy, Don's character is bitter. Even though Don's character is a horrible man, I feel very sorry for him. I think that if you think about each character in the film you'll feel sorry for each of them. I think that is what makes you care about them.

But only if an actor stays true to him or herself.  Do what you want to do because it is what you should do, not for anyone or anything else, but yourself.