Our favorite Jimmy Fallon bits over the last few years have all been musical ones—from Will Ferrell's recent "Tight Pants" song to Stephen Colbert singing "Friday," from Fallon's expert Neil Young impressions to Bruce Springsteen's wiggle-wiggle. Last night, he and Will Smith revealed that their grandfathers (Will "Sunnyside" Smith and James "Fatty Monroe" Fallon) had hosted a 1920's radio show together...and they performed "Parents Just Don't Understand," "Gettin' Jiggy Wit It," and a song that amounted to a big plug for Men In Black III. Watch below, even though this still doesn't make up for the fact the film doesn't have a Will Smith theme song.
And of course, here's a Fallon classic: Neil Young performing "The Fresh Prince Of Bel-Air" theme song.
