After a comedically uncomfortable pause, Letterman's very first words were "I think the longer we just sit here, the more uncomfortable it will make Jay."
To which a more-than-game O'Brien replied (once he stopped laughing), "You know Jay's watching right now." He would later refer to Leno as "a bit of a brat." Ouch.
It's no secret that the two late-night hosts are allies in the War on Leno, and the segment provided them with a rare opportunity to quasi-gang-up on Leno and mock his "reclaiming" of the Tonight Show reigns from O'Brien. Of the 2010 NBC debacle, Letterman said, "I was delighted by everything that happened — except you losing your job."
It was just the latest development in a long-standing contentious relationship between the trio — although, again, Letterman and O'Brien are basically on the same side of the fence. The Leno-Letterman feud dates back to the early '90s, when Letterman, the assumed post-Johnny Carson host of The Tonight Show, was passed passed over by NBC in favor of Leno; it was most recently addressed in a 2010 Super Bowl commercial starring the two hosts alongside Oprah.