By Ken Tucker
Updated February 12, 2009 at 07:01 PM EST

Joaquin Phoenix, his face covered with beard and sunglasses, made one of the all-time weird, ranks-with-Crispin-Glover appearances on David Letterman last night. The audience started giggling as soon as Phoenix declined to acknowledge that he wasn’t behaving very sociably — monosyllabic answers, no smiles, avoiding Dave’s gaze. Finally Dave had to break the ice with a joke: “What can you tell us about your days with the Unabomber?” Check it out:

When Dave asked about the actor’s recently-announced move to become a rap-music performer, Phoenix said, “I’d love to be on the show and perform.” Dave, by now happily irritated at this disastrous interview, said, “You know, that seems unlikely.” By way of farewell, Letterman said, “Joaquin, I’m sorry you couldn’t be here tonight.”

What do you think about Phoenix’s appearance (in every way) last night?