Remember when Jimmy Fallon and Justin Timberlake lost their minds on a “History of Rap” mega-medley co-starring The Roots in the role of world’s toughest karaoke machine? That was awesome. Well this is how we take the old to the new / the new to the old…et cetera! I thought they got up to the present time a little too quick, but then J&J rewound on what maybe the best drunken sing-along rap of all times! Watch.