Joaquin Phoenix's meltdown: Elaborate joke or serious problem?

What's going on here? Months after Joaquin Phoenix's public statement that he's retiring from acting, the troubled star shows up in Vegas to give us a taste of his "rap career," leaving everyone in the audience horrified as he chokes through a song and then falls on his face leaving the stage. Not to mention, he is looking less and less the sex pot that we all knew and loved. Some are speculating that Joaquin (seen here with P. Diddy and Ben Affleck's bro, Casey) is playing a Sasha Baron Cohen-esque prank, but I'm not so sure about this one. He seems like he's on some serious drugs, or something.