MANHATTAN, New York (X17online) - Joaquin Phoenix has returned to the Late Show With David Letterman to tell host, David Letterman, that he's sorry for acting wacky during his last appearance.

Phoenix, 35, appeared on the Late Show last February in character. We now know it was for the mockumentary I'm Still Here. Director Casey Affleck says that Letterman was in on the act the whole time.

However on last night's show, Phoenix tells Letterman:

“I mean, I think that you’ve interviewed many, many people, and I assumed that you would know the difference between a character and a real person, so – but I apologize. I didn’t – I hope I didn’t offend you in any way…”

In response, Letterman jokes:

“Oh, no – oh, no, no, no. I was not offended. I’m telling you, it was so much fun. It was batting practice, you know what I mean? Every one of them was a dinger.”