The 12-12-12 concert to raise money for victims of Hurricane Sandy brought out several legendary bands.  The Rolling Stones, Bruce Springsteen, The Who, Roger Waters of Pink Floyd, Bon Jovi, Billy Joel, Eric Clapton, Paul McCartney and the surviving members of Nirvana.

The concert's organizers wanted Led Zeppelin.

Former president Bill Clinton was enlisted to convince the legendary band to reunite.  The band was in Washington being recognized at the Kennedy Center Honors.

They said no.

Led Zeppelin made occasional appearances in the 1980s at special benefit shows.  Without a ton of rehearsal, the band was never up to par.  They did reunite for one full concert in 2007.  That show turned out well and is featured on the CD/DVD Celebration Day.

Without Zeppelin, the concert still raised over $50 million.