The former "Friends" star took a seat alongside the late night host as he braggingly told the audience about how he walked in on her as she was switching up ensembles in her dressing room.
Recalling the moment with the utmost glee, O'Brien said, "There was a moment there where I knocked on her door and then walked in on Jennifer Aniston when her pants were about half way up... It's the greatest thing that ever happened to me."
Taking it all in stride, Miss Aniston chimed in, "It was quite a moment - I even got a victory dance out of you."
As for her movie, Jen can be seen starring alongside Adam Sandler, Nicole Kidman and Brooklyn Decker in the romantic comedy "Just Go With It" - which hits theaters next Friday, February 11th.