After the performance, some wondered whether Phoenix was carrying out some kind of elaborate ruse. Phoenix's rep, publicist Susan Patricola, released a statement at the end of January saying the actor's rap-star dreams are real and he will continue to pursue them despite naysayers.
"The transition from one career to another is never seamless. It should come as no surprise to anyone that Joaquin came from a musical family, in addition to winning a Golden Globe for his portrayal of Johnny Cash," Patricola wrote in an e-mail. "He intends on exploring his musical interests despite speculative, negative or positive reactions."
Casey Affleck is helming a documentary about Phoenix's foray into music and was in Vegas, along with two other cameramen, shooting Phoenix's performance.
According to media reports, Diddy is producing Phoenix's rap album. At first his rep said she was unaware of his involvement but later she sent ABCNews.com an e-mail saying, "I cannot comment on this at this time."
Several other rappers contacted by ABCNews.com refused to go on the record commenting about Phoenix's new career path.
Snedegar told ABCNews.com that he had his doubts about Phoenix's intentions.
"I'm not sure, to be honest. There were moments when I looked at him and I thought, 'I can't believe he's doing this,'" he said. "Then, there were moments he seemed to be very serious."
Apparently Phoenix was prepared to not be taken seriously. He told People magazine before his performance: "Are there people out there who think I'm a joke? I'm sure there will be. Are there people who think it's going to suck? Probably, but I can't worry about that."
Snedegar said some of the raps' lyrics were about Phoenix leaving acting to become a rapper and growing up in San Francisco, but, for the most part, he had trouble understanding them.
"When he first got on, there was a small sound adjustment -- you had to wait 20 seconds before you could hear him," he said. "Then he started talking, the playback went in and he kept on rhythm. But you couldn't really understand what he was saying. I think he was holding the microphone too far away."
Stunt or not, Phoenix certainly appears serious about his new career. About to go onstage in October for a play benefiting Paul Newman's Hole in the Wall Camps, he told "Extra": "I want to take this opportunity ... also to give you the exclusive and just talk a little bit about the fact that this will be my last performance as an actor. I'm not doing films anymore. … I'm working on my music. I'm done. I've been through that."
The surprises did not end there. Next came Phoenix's bearded, bloated appearance at a party in December.
Hip-hop may seem like an odd fit for Phoenix, who, three years ago, received an Oscar nod for his portrayal of singer Johnny Cash. Not so, he explained to People magazine: "When I was young I liked punk rock music but then I discovered rap. I love the storytelling aspect of hip-hop."
"After all the years of reading scripts and reading lines, this is my chance to do something straight from the heart and put it out there," he told People. "This is me saying this is who I am. This is my story."
But will people want to hear what he has to say?
Snedegar thinks people will tune in, at least initially. About 500 people -- some fans, some skeptics -- turned out for Phoenix's first performance, he said.