The "WWHL" host says he spent the rest of the night reading "the meanest tweets" about him after his CNN gig.
Andy Cohen will be joining Anderson Cooper for CNN's New Year's Eve programming for the second year in a row later this month and, if we're lucky, he'll find out a way to tick off more celebrities when he does it.
"A lot happened on the air. I offended most of our guests," Cohen explained to Fallon. "We had Nicole Kidman and Keith Urban on, live from Nashville, so Anderson's talking to them and I'm like, Nicole, 'When you clapped like this at the Oscars, why did you clap like that?'"
He was, of course, referencing her weird seal clap from the Academy Awards way back in March of that year.
"She said, 'I think there are more important things to be talking about on New Year's Eve' and Anderson's like, 'What are you doing?!'" he recalled. "Everyone was talking about it. It was so bad."
It was pretty bad, as even CNN called Cohen out for getting some "well-deserved shade" from the A-lister.
He said his second blunder came later in the show, during an interview with Celine Dion.
"I go, 'Hey Lady Gaga's coming to the strip, do you have any advice for her' and she didn't want to talk about Lady Gaga," Cohen explained. He added Anderson was, once again, "like, 'What are you doing?!"
To Dion's credit, she didn't seem all that opposed to talking about Lady Gaga, but instead didn't think anyone of Gaga's caliber needed advice from her at this point in her career.
Watch the interview below:
Celine Dion, live in front of a sold-out crowd at The Colosseum, says she wants Anderson Cooper and Andy Cohen to come to Vegas, where it's warm, right now #CNNNYE pic.twitter.com/lXnjxNTfoy