So was Joaquin Phoenix faking it?

That's been the big question looming over I'm Still Here, the new documentary from director Casey Affleck, who is also Phoenix's brother-in-law. The documentary purportedly chronicles the Walk the Line actor's career spiral from acclaimed actor into bloated drug addict and aspiring rapper.

From his strange interview behavior to his fights at one of his godawful hip-hop performances, Phoenix has fueled speculation that he wasn't perpetrating an Andy Kaufman-esque ruse but was actually flaming out in the public eye, squandering what had been a promising film career in the process.

I'm Still Here trailer

Now, in an interview with The New York Times, Affleck says the documentary ... is fake. "It's a terrific performance, it's the performance of his career," Affleck said. Everything in the film was a performance, one played out over two years in the unforgiving media spotlight. "I never intended to trick anybody," said Affleck. "The idea of a quote, hoax, unquote, never entered my mind."

Phoenix is slated to appear on Late Show with David Letterman on Sept. 22, his first time on it since his bizarre, seemingly career-ending appearance on the show back in early 2009.