Cracks me up everytime...
I haven't seen anything mentioned on the boards about this yet...
When you see the scene where Garp and his family are leaving his mom's house, John Lithgow is outside with them, seeing the family off. He walks around the car and kisses Robin Williams square on the mouth, unscripted. It had to be totally impomptu because the reaction Robin gives; he know the cameras are rolling and doesn't want to break the scene. It's !@#$ing classic...