David Edelstein on the nonprank prank:
I'm Still Here does offer the more traditional mockumentary hilarity, like hearing Phoenix rhyme "Joaquin" with "tear out my spleen" and appall Sean Combs--his hoped-for hip-hop producer--with songs of unsurpassed awfulness. We rewatch almost the whole of his jaw-dropping turn on the Late Show, which David Letterman concluded by saying, "Joaquin, I'm sorry you couldn't be here tonight." But Joaquin was, of course, very much there. Later, when he watches the broadcast, he looks genuinely stricken, wondering--as exhibitionists often do, after the fact--if he has permanently deformed his career.