In February 2009, audiences watched with equal parts glee and horror as Academy Award nominated actor Joaquin Phoenix appeared to have a meltdown during an appearance on “The Late Show with David Letterman.” The actor, unrecognizable behind a unruly beard, dark glasses, and a belly, had everyone wondering whether another star was burning out or if it was some sort of hoax. Now the truth has come out. Y Newsday and Takeaway film critic Rafer Guzman has seen “I’m Still Here,” and explains if this was a prank, performance art, or something else entirely.