The crowd at New York City's Madison Square Garden on Saturday night were in for a surprise when Lady Gaga joined U2 on stage and performed a song with the legendary rock band. Lady Gaga walked on stage in her Alexander McQueen shoes to sing "Ordinary Love," a song written by Bono to honor the late Nelson Mandela and included in the biography film Mandela: Long Walk to Freedom. Watch below...

Monsters, what did you think of the performance? Sound off in the comments below!