So the Replacements did Coachella -- the Minneapolis underground rock titans played their first shows in California since 1991 at the massive Indio festival this year. Unfortunately, singer-guitarist Paul Westerberg was plagued with back problems, and had to bring in a ringer to help him sing through much of this past weekend's set. That ringer was Billie Joe Armstrong, Green Day frontman and longtime Replacements devotee, who by all accounts appeared to be having the night of his life. "Dreams really do come true!" he told the crowd, according to Rolling Stone. Armstrong came onstage early in the set, and was wearing the same dorky khaki suit the rest of the members worse. Check the Replacements do "IOU" with their Oakland-dwelling fill-in-singer above.