Sep 21, 2010 09:11 GMT  ·  By

Casey Affleck admitted that his and Joaquin Phoenix’s so-called documentary “I’m Still Here” was just “performance art” but, according to reports, these two weren’t the only ones in on the secret.

Even David Letterman, on whose show Phoenix put in an appearance in February 2009 that could only be described as “odd” and “embarrassing,” knew they were basically playing a prank on audiences.

Entertainment Weekly uncovered an interview with Bill Scheft, the official writer for the Late Show with David Letterman, dated one year ago, in which he leaves no doubt as to how much acting went into the televised interview.

“First of all, that was all an act,” Scheft says of Joaquin’s disastrous appearance. “Think Andy Kaufman without shaving. That’s what he was doing. And Dave knew about it and Dave loved it because he could play along,” the writer explains.

“[Dave] could do whatever he wanted with it. And he did, and it was great television. But I will take credit for the line, ‘I think I owe Farrah Fawcett an apology.’ That line was mine. I gave that to him during the break,” the writer further says.

Letterman agreed to take part in the hoax because he knew it would make for great television – and that it did, as word of how Joaquin was barely able to utter two words in a row made news around the world.

“Dave loves that. He had a ball. He likes anything that’s good television, and he knew that’s good television,” Scheft says.

“I’ve told people that [everyone was in on the joke], and not only don’t people believe me, they tell me that I’m wrong and that [Phoenix] is a schizophrenic and he needs help and he’s going to end up like his brother,” the writer points out.

“I said no. I saw the segment notes. It’s an act. I saw Ben Affleck’s brother taping the whole thing from offstage,” Scheft adds.

At the time the writer gave this interview, the world was too shocked by Joaquin’s behavior to even think that he might be pulling a quick one to make a faux documentary film.

This would also explain why it didn’t cause major fuss back then, as Scheft himself says: because no one would believe him that Joaquin and Affleck had come up with the idea – and that Letterman went along with it.

Below is the video of Phoenix’s appearance on Letterman in February 2009. He’s due to return to the “scene of the crime” tomorrow, September 22, when he’ll also probably explain how he and Dave orchestrated the entire charade.

In the meantime, enjoy.