It said somewhere that audience members actually said it was a joke. During breaks Joaquin was just acting normal and joking around.
I think Letterman is hilarious.

I don't know man. I think he is nuts. He is like that in a lot of interviews but just not that far off his rocker. And before people on here start accusing Dave of being rude, that clip cuts out about half of the interview where Phoenix just sits there and doesn't talk. That clip is just the parts where Dave jokes around. It might be a joke but if it is I don't really get it.

For people that didn't see it.

http://www.youtube.com/watch?v=HXpYk7WGN5Y

I never laughed so hard. I think he's just pulling the biggest joke on everybody.

I am far from interested in celebrity gossip or any of that nonsense, but what I witnessed tonight was one of the creepiest/saddest things I have seen in a while. I am not sure if Phoenix was having a panic-attack, if he is super shy, or if he was playing a joke on Dave, but either way it was creepy. He had a full beard and sunglasses on. He literally said 10 words in the entire 2 segments. Do yourself a favor and youtube that as I am sure it will be up first thing today. Wow!