Joaquin Phoenix looks back at 'horrible' interview

In 2009, Joaquin Phoenix appeared on The Late Show with David Letterman as a character from his film I'm Not Here.

Decades later, he looked back at his appearance on The Late Show, but this time with Stephen Colbert.

The interview at the time sparked mixed responses, and the Joker star now said, "It was horrible. It was so uncomfortable. I regret it. I'll never do it again. I'm so sorry."

"It was strange because in some ways, it was a success, and it was also just one of the worst nights of my life," he added.

Joaquin blamed the film's duration, which lasted over a year, for making him stay in the character longer than he had previously expected.

"We shot for over a year. I did not anticipate that. I thought I was going to be several weeks, maybe a couple months, and what happened was -- because it started out just in my house... and then we started going public," the actor noted, adding, "I had to keep it going."

Elsewhere on the show, Joaquin promoted his upcoming film, Eddington, starring alongside Pedro Pascal and Emma Stone, which will open in cinemas on Friday.