Phoenix's Peculiar Presence

Actor Joaquin Phoenix's 02/11 appearance on the Late Show with David Letterman was memorably eccentric. He wore long hair, a Grizzly Adams-styled beard, and dark sunglasses. He seemed self-absorbed and disinterested with the interview, as he frequently looked down, offereing two-word-answers in between chews of gum. At one point, Letterman jokingly expressed his disapproval of Phoenix's chewing during the interview; to which Phoenix responded by removing the gum, and preceding to stick it to the bottom of Letterman's desktop.
The host and his audienced were hysterically humored by the actor's behavior. Confused by their reaction, Pheonix asked Letterman, "What do you gas them up with?" Late Show Bandleader, Paul Shaffer, laughed mockingly when Letterman asked Phoenix to setup his movie clip, prompting Phoenix to explicitly ask "Are you serious, Mr. Maniacal Laughter".
Addiction Medicine Specialist, Dr. David Pensky, believes Phoenix's appearance suggested "intoxication, or severe psychiatric condition, such as depression". Some have reacted to Phoenix's behavior with concern, others with amusement; those familiar with Phoenix are more likely to fall into the latter category.
He once asked a red-carpet reporter if he had a "large frog in [his] hair", simply because he was bored. He commented on the incident saying "I made it up. It entertained me. I do a lot of that kind of thing." That incident, years ago, similarly left some thinking he was insane.
His latest incident has even more signs of a hoax. First of all, he breaks character twice during the interview: he laughs when the host expresses his disappointment that the actor did not show up; and once the interview is over, Phoenix jumps up and takes off his glasses, talking to Letterman more freely. If that were not telling enough, he and friend Casey Affleck are reportedly working on a documentary about the actor's alleged transition from acting to rapping.