I discovered a game a while back in which Letterman played Kasparov
(and lost - no surprise!) I don't know the context though it appeared
to be a serious game:
It was deadly serious. Fischer was very surprised to be beaten. The
opening was a Sicilian Sozin as I remember. Fischer, as white was
pretty torn up. He said to Ade Edmondson that he was going to have a
really good long think about the game, as clearly something had gone
seriously wrong.