The surprise appearance on the group's "Innocence + Experience" tour began when Fallon was called on stage from his spot in the crowd on the floor, where he held up a sign that read "singer with a broken finger."

"I'm a big fan of Irish people that fall down and hurt themselves," said Fallon when he arrived on stage with an introduction by Bono. "So you're like a mentor to me, brother. Edge, what you did a couple of weeks ago falling off the stage was classic, brother. I'm happy to be a part of the club."

The reference calls upon Bono's bicycle injury in New York's Central Park last November, as well as guitarist The Edge's fall off stage during the tour's opening night in Vancouver on May 14.