Chalk this up to Duets We Never Thought We'd See.
No, not Chris Pratt and Jimmy Buffet... though also likely qualify for this label.
We refer instead to Jon Hamm and Zach Galifianakis.
The two stars kicked off the 2015 Bonnaroo Music Festival over the weekend by singing their own version of "We Are the World" at a 1980s throwback party.
You must watch this unexpected duo shock the audience above.
Galifianakis and Hammonly only stuck around for one song, but the rest of the SuperJam party was star-studded.
Among the names performing at the event were Chance the Rapper, Pretty Lights, DMC and Corey Feldman, who presented a screening of "The Goonies" at the festival.
That's nearly as awesome as this duet!