U2 are racking up star-studded guest spots at their ongoing eight-day residency at Madison Square Garden in New York City, and last night (July 26), Lady Gaga was the latest to enter the stage with the Irish rockers.

The pop superstar sat in on piano and joined frontman Bono for a duet of “Ordinary Love,” the Irish rockers’ contribution to the 2013 Nelson Mandela biopic, Mandela: Long Walk to Freedom. Check out fan-shot footage of the performance in the video up above and a pair of photos below:

Last week, Jimmy Fallon and the Roots appeared with U2 during the first night of their MSG residency. The late-night host and his Tonight Show house band joined U2 on two Rattle and Hum cuts: Fallon collaborated with the band on “Desire,” while the Roots were featured on “Angel of Harlem.”

U2’s MSG takeover will conclude this Friday (July 31). Then, they head abroad for the European leg of their Innocence and Experience tour. Check out their complete itinerary on their website.