Joaquin Phoenix’s I’m Still Here is still making waves, and most movie reviewers are still scratching their heads. Phoenix scored plenty of huge headlines when he purportedly walked away from his acting career to pursue rap, but it was his David Letterman appearance that really got people talking.

Ben Stiller famously impersonated Phoenix at the Oscars, appearing on stage in a full beard to poke fun at Joaquin’s rugged look. But Phoenix says that Stiller, along with several others who appeared in the pseudo-documentary, was in on the joke.

In the audio commentary of the DVD, Phoenix and collaborator Casey Affleck reveal that P. Diddy “took direction well” and played his staged scenes admirably. Stiller’s appearance in the movie was filmed after his little Oscar joke, but the film was edited to make it look like he offered Joaquin a film role before the glittery Hollywood awards show. “He was totally game,” says Affleck.

Phoenix even says that his onstage fall, an infamous YouTube moment, was a joke. He channeled Chevy Chase to fake the tumble, inspired by the actor’s physical comedy.

Natalie Portman and Edward James Olmos, who appear in the film, were also in on the joke.