Jimmy Fallon's impeccable impression of Neil Young has become one of the host's best recurring bits since he started hosting Late Night, with his version of the rock icon performing straight-faced Young-style versions of everything from the theme song to the Fresh Prince of Bel Air to Willow Smith's hit "Whip My Hair." On last night's episode of the show, Fallon's Young was joined by the real David Crosby and Graham Nash for a sad, beautifully harmonized folk rendition of Miley Cyrus' "Party in the U.S.A." that manages to make the joyful tween anthem sound like a vintage Sixties protest song.