Because Justin Timberlake can no longer do any wrong (never forget!), the 20/20 man spent the last four days as an in-house guest on Fallon. On Friday, the two teamed up to spit Part 4 of their highly entertaining "History of Rap" series. The pair hits the classics—the Fat Boys, Biggy, Kurtis Blow—but they really come alive when performing "No Sleep Till Brooklyn." And in a nice touch, Fallon chooses to go with an MCA line. Check it out.