But the ensuing Casey Affleck-directed documentary, "I'm Still Here," makes Phoenix look as serious about his rap career as "Borat" was about benefiting the glorious nation of Kazakhstan.
However, the Academy Award nominee does highlight some interesting truths about life as an oh-so-serious-actor beneath his adopted bushy beard.
“I don’t want to play a character anymore… some dumb funny puppet,” Phoenix explains in the film, before slamming his (former) actors as falsely believing they are being “all creative, when acting isn’t creativity at all."
But in his “transition” into a new music career, the seemingly lonely, pot-bellied 35-year-old epitomizes – or does he satirize? – the lifestyle typically associated with rock stars and movie stars.
Phoenix snorts cocaine, (or is powdered sugar?) has a wild night with hired hookers, (or are they hired extras?) and treats his assistant poorly. Said sober-living employee, who is accused in the film of selling insider information to the tabloids, eventually seeks revenge by defecating in Phoenix’s mouth as he sleeps.
The former actor’s antics and Affleck’s “direction” can be clever, yet more often come across as scripted, not spontaneous.
Nonetheless, Affleck is standing firm that the film is legitimate. "I can tell you that there is no hoax. That never even entered into my consciousness until other people began to talk about the movie,” Affleck told reporters at the Venice Film Festival this week, where "I'm Still Here" premiered.
“I’m Still Here” is also laced with references to Phoenix’s childhood, his fear of jumping off a cliff into a river in the family’s Panama vacation home, and footage of the Phoenix kids performing in a Westwood talent quest. Although there is no direct reference to brother River Phoenix’s fatal drug overdose outside the Viper Room in 1993, one can’t help but be disturbed by Joaquin’s amped up drug use as reference to the sinister side of stardom, a life he chose to lead but now looks to be trying to escape.
And if you thought Phoenix was immune to all the jokes about his “homeless” guise following his "retirement," think again. In the film, the ex-actor constantly Googles himself, wincing at the blogs and bad press, and looks distraught when Ben Stiller dresses up as him and mocks his appearance at the Oscars.
Phoenix also watches reruns of his now infamous 2009 interview on “The Late Show” with David Letterman in which he can barely string together two sentences. But again, was Phoenix putting on an act with Dave? Because a source at the taping of the Letterman show told FOX411.com that while Phoenix appeared anxious and annoyed during the interview, the vibe was quite different during the commercial breaks, as he and host were chatting and laughing.
After 108 minutes of beyond plausible insanity, complete with following Diddy around the country in desperation for him to hear his music, and making snow angels in Central Park, the question remains: is this really the last time we’ll see Phoenix on the big screen? While Phoenix’s hip-hop music career is most likely dead in the water (we pray), was the film just a two-year social experiment, or has Phoenix really quit acting for good?
The “Walk the Line” star has no future projects listed anywhere, so if he is going to work again, he's very good at keeping it a secret.
Hollie McKay has been a FoxNews.com staff reporter since 2007. She has reported extensively from the Middle East on the rise and fall of terrorist groups such as ISIS in Iraq. Follow her on twitter at @holliesmckay