Kim Kardashian & Calvin Harris Light Up J.Lo's Pre-Birthday Party

Ageless Jennifer Lopez turns 47 years old today, and she celebrated with a star-studded pre-birthday party last night in Las Vegas.

First, she gave her all in a performance of her "Jennifer Lopez: All I Have" show, which was attended by Cristiano Ronaldo, L.A. Reid, Iggy Azalea, John Stamos, and French Montana.

Even more interestingly, Kim Kardashian — currently feuding with Taylor Swift — showed up, as did Swift's ex, Calvin Harris. Both Kim and Calvin have recently posted clips of themselves singing along to Kanye West's Taylor-bashing tune "Famous."

The intimate after-party, hosted by Jennifer's longtime manager Benny Medina and Beau Smart in her Caesar's Palace villa, seemed to be governed by two rules: (1) You must be famous, and (2) You must take lots of selfies.

Jen's pre-birthday outfit was a brown, form-fitting number with almost more skin than material showing. She was looking very confident in her barely-there ensemble, pausing to playfully dance next to Calvin for a short Instagram video.

People magazine reports Jen was surprised as she entered the party to be embraced by Kim, and presented with a big birthday cake with four candles that Kim helpfully took out of her hands: