"We hadn't spoken for a long time," O'Brien said, "and he just called to basically say, 'I haven't checked in on you. I just wanted to make sure that we were good.'"
Letterman was concerned that some of the jokes he told during the whole Leno-pushes-Conan-out-of-"The Tonight Show" melodrama might have bothered O'Brien. Although, clearly, Letterman was taking aim at Leno, not O'Brien.
"I said, 'We've always been good,'" O'Brien said. "I have a lot of respect for that guy. And I said, 'You didn't owe me a phone call, but I appreciate it.' And then he chatted about other silly things, and that was it. So it was not a lengthy phone call. He's not a blabbermouth, but it was nice. It was just nice to get the call.
"It was nice to get it, but I wanted to reassure him that he didn't owe me any call or anything like that."
While he was pleased to hear from Letterman, O'Brien has still not heard from Leno. Nor does he have any desire to talk to the guy who took "The Tonight Show" away from him.
"No, I don't think so," O'Brien said. "There's nothing to be figured out. We all know the story, and we all know what happened."
Yes, we all know that - just as he did almost 30 years ago when he outmaneuvered Letterman to become Johnny Carson's successor - Leno acted badly. Only in this case, he's finally been called on it. And his ratings have taken a major hit as a result.
And O'Brien, who's moved successfully to TBS, just wants to put it behind him at this point. Without listening to Leno trying to justify his actions.
"Life is short," he said. "I've got kids and a family. I've got a life to live. And I'm really happy here. So I don't think about it too much.
"I'm sure he's busy."