Taylor Swift and Nelly joined forces to perform together at Karlie Kloss' birthday party this weekend.

While attending Kloss’ joint birthday party with oil industry heir Mike Hess in the Hamptons, the 41 year old rapper pulled 26 year old Swift up onstage to help sing his 2002 hit “Dilemma.” Swift sang and danced her way through Kelly Rowland’s parts while wearing a tiny black top, a black skirt (which, of course, covered her belly button) and white sneakers.

This isn't the first time the pair have performed together as last year, Nelly was a guest at Taylor's gig in St. Louis, Missouri, and the two, along with Haim, sang his single 'Hot in Herre'.

Karlie turned 24 on August 3, and Taylor marked the occasion by praising her an an "exquisite person" and an inspiration.

Wearing her hair with curls for the first time in a while, Swift took us back to her “Tim McGraw” days.

Sharing a selfie of them both, she wrote:

"I LOVE YOU KARLIE. You're such an exquisite person, always trying to make things better for others. Every day I'm inspired by how giving, loving, and thoughtful you are. Happy 24th Birthday!!! @karliekloss."

And though they couldn't spent the day together, the Bad Blood' hitmaker ensured she was able to chat to her friend via FaceTime.

The singer caused a bit of a stir online when she kissed birthday boy Hess on the cheek during the performance (see video). Tom Hiddleston need not worry, as it looked like friendly peck on the cheek.