Casey Affleck admitted a couple months ago that Joaquin Phoenix’s retirement from acting, pursuit of a hip-hop career and descent into apparent insanity---and Affleck’s filming of this transition---was an elaborate gag. The real-or-fake question is no longer in play, but the duo’s ballsy gamble still yields big results, among them Phoenix’s genuine transformation from super-serious dramatist to ace deadpan comedian. The actor commits completely to his portrayal of a bloated, drug-addled and delusional narcissist who leaves people dazed, confused and amused in his cruel wake. It’s all here, from the dreadful rap performances to the infamously incoherent *Letterman* appearance, and it’s as riveting as it is hilarious. “I just want to be triumphant,” Phoenix moans in the film’s early moments. That he is. –Matt Semansky