Justin Timberlake has been having a lot of fun paling around with potential future Tonight Show host Jimmy Fallon during his week-long residency on Late Night With Jimmy Fallon. Previously, they performed a swingin' barbershop quartet rendition of "Sexy Back," but saved the best for last: below, watch the two perform the fourth edition of their effervescent "History Of Rap," with bits of the Beastie Boys, Slick Rick, Run DMC, Salt N Peppa, Missy Elliott, Eminem and more.

In case you haven't seen it (or just haven't seen it lately), here are the first three parts put together.