Oscar winner Joaquin Phoenix (“Joker”) was the guest of honor on “The Late Show With Stephen Colbert,” marking his first appearance on the late-night staple since his infamous 2009 interview with Dave Letterman and on-air apology the next year.

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The Oscar winner memorably appeared on Letterman’s “Late Show” in character (shaggy hair, untamed beard and all) from his mockumentary “I’m Still Here,” which documented his life after the spoof announcement that he was retiring from acting to pursue a hip-hop career. The interview, some of which was used in the film, was incredibly awkward and led the public to believe Phoenix was having a mental breakdown.

But Phoenix admitted that the interview itself was “horrible,” adding: “It was so uncomfortable. I regret it, I’ll never do it again. I’m so sorry.”

After they laugh, Colbert told Phoenix, “I don’t know if [Letterman’s] watching.”

The actor, who stars in Ari Aster’s new movie “Eddington,” apologized to the late-night host when he came back on “The Late Show” in 2010. “I hope I didn’t offend you in any way,” he said. “You’ve interviewed many, many people and I assumed that you would know the difference between a character and a real person, but I apologize.”

Phoenix concluded: “It was strange because in some ways, it was a success, and it was also just one of the worst nights of my life.”

Watch Phoenix’s full interview with Colbert below.