Phoenix has a rep for playing strange, complicated characters. That includes a rapping, wasted, Unabomber beard-wearing version of himself in the Casey Affleck mockumentary, I'm Still Here.
Fans and haters of Jared Leto's Joker from Suicide Squad should know that Leto isn't affected by this move. The still-untitled movie will reportedly be a standalone production. Fans of Leonardo DiCaprio will be disappointed—though he was originally in the running, reports indicate that's a non-starter.
Social media reactions seem pretty positive. This is probably due to Phoenix's intense reputation as an actor who never does a half-ass job in a role, no matter how bad the script.
As several reports pointed out, Phoenix has backed out of roles in other comic book movies, such as Doctor Strange. Let's hope he hangs on this time. If there was ever an actor who could totally own such an insane role, he's the man.