Remember when Joaquin Phoenix was this thoroughly loveable, mysterious, edgy and strikingly handsome force to be reckoned with?

And then he stopped shaving (and probably showering), buried his career and picked up a mic?

The bizarre transformation was so intense that it would have been a crime not to put it on tape. And that’s exactly what good friend and director Casey Affleck did.

"I wanted to explore what I thought would be an interesting period in his life. He said he didn't want to act anymore, he wanted to try doing music, and that, right there, says something's going to happen... I had no idea what exactly was going to happen and all that would unfold and every day I spent with him on this journey,” Affleck, who is married to Joaquin’s sister Summer, told ABC News. “I made for this unbelievable, one-of-a-kind movie.”

Read Joaquin Phoenix: Crazy Smart or Just Plain Crazy?

I'm Still Here: The Lost Year of Joaquin Phoenix opens nationwide September 10. Check out the trailer below, and read on to relive the madness: