He's either crazier than a brick ****house or one hell of an actor, the verdict is still out.
It's all a joke/hoax, Casey Affleck's doing a documentary about a actor losing his mind and dropping off the map, going to be at Sundance for the hippies and mormans.
Untitled Joaquin Phoenix Documentary (2010)
I think Dave was in on it, and the crowd, or they wouldn't have been laughing like they were, and would have been scared to death instead.