Lady Gaga Performs With Mariachi Band at Her Surprise 25th Birthday Bash

Lady Gaga celebrated her 25th birthday doing what she does best -- working.

At a surprise birthday bash, thrown by her friends at LA's Mexican hot spot La Cita, Gaga got on stage and performed her smash hit 'Born This Way' with the establishment's festive and talented Mariachi band. It was just another example of the universal nature of the song. It can be twisted into a country ballad or performed by a Mariachi band and still retain its spirit.

According to Us Magazine, 60 of Gaga's closest friends gathered and were on hand feasting on several birthday cakes, as the singer took the stage -- dressed in all black with a towering beehive of hair atop her head -- singing songs by Motley Crue and Madonna.

A source told Us that Gaga was "onstage for most of the night performing for all her friends. No one knew she was going to go up there and perform with them, I think she just loves to be on stage and doing what she does so well." Since the stage is Gaga's most natural habitat, it makes sense that she would provide the entertainment, even on her birthday.

When she wasn't singing, she was the consummate birthday girl, mingling with guests who were there in her honor. "She was walking around saying hi to everyone," added the source. "It was an amazing night."

Watch Gaga Perform With the Mariachi Band