Casey Affleck: Joaquin Phoenix Movie Is No Joke

May 11, 2010 — -- Remember when Joaquin Phoenix said he was giving up acting to take up rapping and transformed from a clean cut, Oscar-nominated thespian into a bearded, perpetually sunglasses-clad punchline?

He raised a lot of questions: Why would he give up on film? What does he know about rap? This has to be a joke, right? And what's he hiding in that beard?

According to Casey Affleck, who just finished directing a documentary about Phoenix's metamorphosis, his piece of cinema will answer them all, from Phoenix's roots in rap to that bizarre 2009 appearance on "Late Show With David Letterman."

Affleck talked about "I'm Still Here: The Lost Year of Joaquin Phoenix" on ABC News Now's "Popcorn With Peter Travers."

"I wanted to explore what I thought would be an interesting period in his life," Affleck said. "He said he didn't want to act anymore, he wanted to try doing music, and that, right there, says something's going to happen ... I had no idea what exactly was going to happen and all that would unfold and every day I spent with him on this journey."

"It ended up being more and more fascinating, more and more things happened that were both in the public spectacle and a very private internal implosion that I got to witness," Affleck continued. "It made for this unbelievable, one-of-a-kind movie."

A key moment in Affleck's documentary is Phoenix's appearance on "Late Show," in which Phoenix scratched at his (now shorn) scraggly beard, cursed at Letterman and stuck gum on the host's desk.

"You'll find out what was happening in his life in that period -- what was going on before he went on, what was going on afterwards," Affleck said about the bizarre interview. That episode -- along with a couple of sub-par 2009 rap performances in Las Vegas, in which Phoenix fell off the stage and got in a fight with a fan -- was strange enough to make critics wonder if Phoenix faked his whole aloof persona, but Affleck said that's not the case.

"I understand there were all these different reactions to what happened on the Letterman show; millions of people saw on YouTube and wrote about it and talked about it all over the place but most of them were wrong," Affleck said. "[Phoenix's motive] was nothing that anybody ever guessed."