Mad Men actor Jon Hamm and comedian Zach Galifianakis surprised fans at the Bonnaroo SuperJam on Saturday night.
Hamm and Galifianakis kicked off the Bonnaroo's 2015's Throwback SuperJam Dance Party by holding each other and playfully singing USA For Africa's "We Are The World."
Hip-hop artist Chance The Rapper, singer SZA, Jurassic 5's Chali 2na, electro-indie duo Cherub, Metallica bassist Rob Trujillo DMC of Run-DMC, comedian Reggie Watts were also apart of the SuperJam.
Hamm and Galifianakis also performed together inside Bonnaroo’s comedy tent prior to their sing-a-long.
Watch Hamm and Galifianakis perform below: