Lady Gaga joins U2 on stage at Madison Square Garden

Pop sensation Lady Gaga surprised the audience during U2'S Residency at New York's Madison Square Garden by appearing onstage for a duet.
The "Bad Romance" hitmaker appeared during the Irish rockers' fifth night of their eight-date residency, wearing only black undergarment and towering heels as the crowd went wild, reported Billboard magazine.
Gaga, 29, played piano and joined Bono for an acoustic duet of the band's track Ordinary Love, which was written to honour late South African activist Nelson Mandela.
U2 shared a picture of the moment on their official Instagram page after the show and wrote, "All hail Her Gaganess".

The group previously invited The Roots and US TV host Jimmy Fallon onstage during their residency, which ends on July 31.