Green Day's Billie Joe Armstrong made a surprise appearance at Coachella Friday night.

Armstrong joined The Replacements for most of their set on vocals and guitar, helping out ailing frontman Paul Westerberg, who was reportedly suffering from back issues and sang most of the band's songs sitting on a couch. At one point, Armstrong -- obviously thrilled to be playing with one of his biggest influences -- told the crowd, "Dreams really do come true."