Inside Music's Biggest Mash-Up

Justin Bieber and Snoop Dogg's hand jive, Nicole Richie's meet and greet with a JoBro – and more surprise pairings from the "We Are the World" sessions

5 of 10

ALL-STAR CHORUS

ROLL OVER photo to reveal more!

The recording session isn't just for professional singers! Funny guy Vince Vaughn raised his voice along with rapper-turned-NCIS: Los Angeles star LL Cool J (left) and Oscar nominee Jeff Bridges.