Taylor Swift's role as Allison during "The Californians" sketch on the 40th anniversary episode of Saturday Night Live wasn't nearly as entertaining as her post-show performance with Paul McCartney.

Sure, fans are only treated to this clip of her singing "Shake It Off," but the room is clearly loving it. McCartney plays bass and tries to sing along while afterparty host Jimmy Fallon goes crazy on the corner of the stage. Toward the end, even he can't help himself. The former SNL cast member grabs a mic and starts to sing. Someone get that man some Swiftamine!

"Shake It Off" is Swift's first single from her 1989 album. She also turned up during the actual episode, playing a pivotal role in a sketch that involved Bradley Cooper, Betty White, Bill Hader and more. The highlight of that sketch was White and Cooper making out like they were in 50 Shades of Grey.

See Taylor Swift and More as Kids: