Right after her sold-out concert at Fenway Park in Boston, Gaga went across the street to the House of Blues and joined her friend Brian Newman onstage during his own show. Gaga only sang one song, the jazz classic "Coquette," but then joined the audience to watch the rest of the show.

"I was hoping you'd stall so I could get a drink in me before I got up here," Gaga, who had just become the first woman ever to headline Fenway, told Newman onstage while performing.

Enjoy videos of Gaga performing at the House of Blues and Fenway park below!

Plus, click here to listen to Brian Newman's brand new single "Sunday in New York."