This photograph above shows Spinal Tap's July 7 Reunion Performance at Live Earth London at Wembley Stadium with "Every Bass Player in the Known Universe." Bass players from numerous band joined Spinal Tap for their song "Big Bottom." Foo Fighters, David Grey, Block Party, James Blunt and the Beastie Boys took part in the epic jamfest. Live Earth was a 24-hour, 7-continent concert series that took place on 7/7/07, bringing together more than 100 music artists and 2 billion people to trigger a global movement to solve the climate crisis. You can watch video from the Live Earth concerts on MSN at http://liveearth.msn.com/.
Here is a YouTube clip from Spinal Tap's Army of Bassists (hat tip Boing Boing.