This clip is from Waiting for Beckett. It is the only place I can find any of the Steve Martin, Robin Williams production. You will find it between 4:06 and 10:40, but do yourself a favor and watch the whole thing. Not insignificantly, it was directed by Mike Nichols and also featured Bill Irwin, F. Murry Abraham, and Lukas Haas. I – and it seems many others – would love to see the whole thing someday, but it is nowhere to be found.
Williams and Martin appear to nail the comedy in Beckett. I get the feeling Williams could play every character brilliantly (though I don’t like his improv in the scene – so wrong on so many levels). Aside from the criticism (“Critic!”), their attempt at playing Beckett is intriguing to say the least.
Aha! I just found this:
It seems the pre-Godot Robin Williams agreed with me about improvising on Beckett’s text.
Here is part I of the documentary, Waiting for Beckett. Just play the youtube wild goose chase after that to find the other parts. It is excellent – well worth suffering through the poor quality of the copy.