David Letterman definitely knew something was off. But despite what his writer previously reported, he did not know what Joaquin Phoenix was up to last year.

That’s why I’m Still Here actor – who reunited with Letterman Wednesday for the first time since February 2009 – felt it necessary to make amends for his little stunt.

“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,” the two-time Oscar nominee said.

“Oh, no – oh, no, no, no, I was not offended,” Letterman replied. “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.”

“Well, we’d hoped to come on a talk show and I was looking for a beat down, and I got one ... I want to thank you for that,” Phoenix laughed.

Of course, Dave – who always knows how to make someone squirm – had to raise the compensation question.

Although Late Show execs would have normally required a movie studio to license footage of their program, Phoenix’s lawyers insisted the clips from his last visit should have been considered “fair use” since it was being used in a “documentary.” But since we all now know the truth – Letterman (rightfully) thinks he should get paid.

“Now you owe me a million bucks,” Dave claimed.

An uncomfortable Joaquin then replied, “We’ve made 75 cents on this movie.”

Believe it or not, that’s something Joaquin’s actually not lying about.