There's something about David Letterman's crotchetiness that makes celebs want to go on his show and irritate him. There was Crispin Glover who did a high-kick to his face, and most recently Joaquin Phoenix who slurred throughout his interview and then stuck his gum underneath Letterman's desk. (Not cool.) Here's an interview from the '90s (?) with Cher trying to explain why it took her so long to agree to go on the Letterman show. Around 3:15 he presses her for details, and around 3:30 I imagine he regrets it when she answers with brutal honesty. I suspect it was shows like this that turned Dave into the full-on curmudgeon he is today. . .