Hamm And Galifianakis Perform Festival Duet

Mad Men and Hangover stars Jon Hamm and Zach Galifianakis surprised festival-goers in the US by performing a duet of We Are The World on stage.

The actors were at the Bonnaroo festival in Tennessee when they joined in the event's annual SuperJam, which is a late night concert where artists cover classic songs.

The pair enthusiastically belted out the 1985 USA for Africa charity single which originally featured Michael Jackson, Ray Charles, Bruce Springsteen and Cyndi Lauper.

The rendition was filmed by a member of the audience who posted it on Instagram.

Earlier on in the evening, Galifianakis introduced Scottish band Belle and Sebastian on to the stage and proceeded to throw gummy bears into frontman Stuart Murdoch's mouth.

Billy Joel, Mumford & Sons, Kendrick Lamar and Deadmau5 also performed at the event.

Hamm said goodbye to Don Draper last month as the seventh and final season of Mad Men came to end.