This weekend, Lady Gaga made a surprise stop in Chicago at the Pitchfork Music Festival in Union Park. It’s not exactly her usual kind of venue — this year’s headliners included Feist, dark female singer Grimes, and Vampire Weekend.

Even Pitchfork’s founder and CEO, Ryan Schreiber, was taken by surprise when Mother Monster turned up. He took to Twitter and Instagram to share his sighting.

WTF Lady Gaga is at Blue Stage for Kendrick! instagr.am/p/NHiFmAq4ly/

— Ryan Schreiber (@ryanpitchfork) July 15, 2012

Gaga turned up on Sunday to show support for her friend and labelmate, Kendrick Lamar. Speculation was rampant across Twitter about whether the pop star would be taking the stage, but the closest she got was standing on the stage to watch while Lamar performed.

Yup, Lady Gaga IS watching Kendrick Lamar side stage at Pitchfork Fest. Just twirled around while he did “The Recipe.” – @jasonlipshutz #p4k

— Billboard(@billboard) July 15, 2012

Lamar told The Source, “That’s a real good friend… a real good friend.”

The two have no plans to collaborate at present, at least not that they’re revealing. Lamar further said, “God willing…for now I just like the friendship thing.”

Lamar’s debut album, m.A.A.d city will drop on October 2. Check out his single, “The Recipe,” featuring Dr. Dre, to get a taste of what Gaga’s such a big fan of.

-Courtney E. Smith, CBS Local