Joaquin Phoenix says he regrets his infamous interview with David Letterman, in which he remained in character for the entire, awkward conversation.

He appeared in character for his Casey Affleck-helmed mockumentary 'I'm Still Here', which saw Phoenix quitting acting to pursue a hip-hop career.

J oker star Joaquin Phoenix recently returned to The Late Show after a whopping 15 years — but something else also happened: he apologized for his infamous David Letterman interview from 2009 that took place on the show before Letterman turned the reins over to Stephen Colbert.