Fans watching Semi Precious Weapons in Chicago last Friday got more than they bargained for.

During the group’s set at Lollapalooza, the band was joined onstage – and off-stage – by Lady Gaga.

The “Bad Romance” singer not only hit the drums during a performance of “Magnetic Baby,” she hit the crowd with singer Justin Tranter.

In the video above, you can see Gaga crowd surfing with help from the excited festival attendees.