The actor was promoting the mockumentary 'I'm Still Here' when he delivered one of the strangest interviews ever recorded for late night television.

An interview gives audiences insight into an actor's upcoming project. One of the most effective ways to promote a film, show, album, book, and more is by appearing as a guest on a talk show. There was a time when everyone wanted to book a spot on TheLate Show with David Letterman;

J oaquin Phoenix has apologized for his controversial 2009 appearance on The Late Show with David Letterman. Phoenix, in character for his role in the mockumentary I'm Not Here, answered Letterman's questions with mumbles and one-word answers, leaving the host and the audience confused.