Surprising hardly anyone, Casey Affleck (Ben's brother) has admitted that his I'm Still Here documentary about the alleged career tailspin of Joaquin Phoenix was a hoax. However, in an interview with The New York Times , Affleck said, "The idea of quote, hoax, unquote, never entered my mind." While, as the newspaper observed, most mockumentaries "wear their foolishness on their sleeves," Affleck said that with his film, "We wanted to create a space. ... You believe what's happening is real." Such was the case, it would appear, when Phoenix guested on David Letterman's show, with Letterman winding up by remarking, "Joaquin, I'm sorry you couldn't be here tonight." Affleck told the Times that Letterman was unaware that Phoenix was performing an act, one, he said, that he will not be reprising when he returns to the show next Wednesday. But in an interview in today's (Friday) Los Angeles Times , an unnamed industry agent predicted that Letterman "is really going to Take That poor guy to the cleaners."