Irish rock band U2 concluded its eight-night concert at Madison Square Garden in New York City on Friday night with a special appearance from Bruce Springsteen and treating the audience with a special two-song set, Billboard reported.

Springsteen sang "I Still Haven't Found What I'm Looking For" and a cover of "Stand By Me" by Ben E. King, a song that the rocker first performed with U2 onstage at JFK Stadium in Philadelphia on Sept. 25, 1987.

Springsteen watched the show with former U.S. president Bill Clinton and wife Hilary. Fans were not assured that the Boss would make an appearance during the concert, but lead singer Bono did leave a few clues that he was going to, Rolling Stone reported.

The most notable clue was when Bono sang six seconds of "Hungry Heart," which was one of Springsteen's well-known songs that he originally wrote for The Ramones, and then a crew placed an additional mic stand at the closing moments of "Where The Streets Have No Name."

Introducing the special guest, Bono said: "Earlier, when I busted myself up here in the city, we had a gig in Times Square for Red and this man showed up and delivered. The chairman, the Boss. Mr. Bruce Springsteen."

Springsteen joins the long list of performers who have guested with the band during the North American leg of its tour, including Lady Gaga, Jimmy Fallon and the Roots and Paul Simon, EW reported.