Here's Joaquin Phoenix on David Letterman later tonight, either stoned out of his mind or just medically catatonic (or both). Letterman makes several heroic efforts to politely prompt Phoenix before ruthlessly mocking him.

Again, celebrities: Dave doesn't want to rip you to shreds on national television, but if you're not going to help him fill the 10 minutes or whatever, he has no choice.

This particular trainwreck was predictable. The movie star has been generating embarrassing tabloid headlines for weeks with his slurry rap performances, to the point where some of his associates started insisting the whole thing was a joke. Phoenix then had to assure everyone he was serious.

Phoenix also announced that Two Lovers, the film he was sent on Letterman to promote, would be his last, since acting now bores him. So even if he hadn't been behaving erratically, Phoenix was not likely to have brought much enthusiasm to Late Show tonight.

Phoenix certainly knows how to turn on the late-night charm when he wants to; here he is on Letterman on 2005, sounding coherent and humorous (and wearing the same suit!) while promoting Walk the Line:

This time around, Phoenix has either come unhinged again, or wants the world to think he has. It's possible he's engaging in some performance art for the documentary his brother-in-law is making about him. But on Letterman, at least, where Phoenix grew increasingly hostile toward the host and crowd, the celebrity doesn't appear to be doing that sort of cool-headed calculation and planning.

At the end of the interview, Letterman says he owes an apology to Farrah Fawcett. Fawcett was considered his all time most disastrous guest — until now at least. Here's her 1997 appearance:

Best moments from tonight's show are above; the full CBS highlights reel is below: