Joaquin Phoenix made a memorable appearance on "The Late Show With Stephen Colbert" this past Tuesday, revisiting the aftermath of his notorious 2009 interview with David Letterman that still haunts him.

In that infamous segment, Phoenix appeared with a disheveled look, complete with shaggy hair and a scruffy beard, fully embodying his character from the mockumentary "I’m Still Here." This bizarre promotion followed his spoof declaration of retirement from acting to pursue a hip-hop career, leading viewers to suspect he was in the midst of a mental breakdown.

During his chat with Colbert, Phoenix admitted that his intention had been to provoke a strong reaction not only from Letterman but from the audience as well. He clarified, "I did a pre-interview in character and realized it was a little silly, so I contacted them to say, ‘I want to do this in a way that’s really dangerous.’" However, he also acknowledged, "The interview was horrible. It was so uncomfortable. I regret it; I’ll never do it again. I’m so sorry."

Colbert, sharing a light moment with Phoenix, quipped, "I don’t know if Letterman’s watching," to which Phoenix replied, "He might be, and I just need to say, I’m sorry." Back in 2010, when he returned to "The Late Show," Phoenix had already expressed his apology, stating, "I hope I didn't offend you in any way. You’ve interviewed so many people, so I assumed you’d know the difference between a character and a real person, but I apologize."

Looking back, Phoenix reflected on his bizarre Letterman appearance, admitting, "In some ways, it was a success—but it was also one of the worst nights of my life." As Phoenix continues to navigate his career, including his latest role in Ari Aster's film "Eddington," this infamous episode serves as a haunting reminder of the blurred lines between art and reality.