Jimmy Fallon had a special guest on "Late Night" last night: "The Boss" himself, Bruce Springsteen! Fallon was thrilled to have him on the show, and so was Fallon's alter-ego Neil Young. Fallon ended up doing his notorious impression of Young while Springsteen joined him in a slow, acoustic version of Willow Smith's hit song, "Whip My Hair." Springsteen also wore a costume, although it was pretty much one of himself in the 70s. Listen to their heartfelt rendition of the season's hottest jam below.