The epic moment went down over the weekend at a Saturday Night Live after party. They were there celebrating the show's 40th year, and that's when the former Beatle got up on stage to shake it off with T-Swift.
Tay and Paul weren't the only ones on stage, either. They were joined by Jimmy Fallon, Jim Belushi, and Dan Aykroyd.
"Bring it #fallon #McCartney #Swift #Akeroyd #belushi #SNL40 Plaza Hotel #nyc 🗽❄️🗽🎶🎶🎶🎶🎶🎶🎶," co-chairman and co-owner of The Palm Restaurants Bruce Bozzi captioned a pic of the group getting down.
According to an audience member, Taylor was having a blast during the whole performance. Unlike when she was at the actual show, and was caught rolling her eyes at someone.
"Taylor was dancing and blowing kisses to the girls from HAIM," the bystander shared to Us Weekly about the mini-concert. Watch a video of the whole thing below!