The crooner swings by to help Fallon close out his first week as host of The Tonight Show

Break it down, J.T.!

Justin Timberlake stopped by The Tonight Show Friday to support pal Jimmy Fallon as he closed out his inaugural week as the brand-spankin’-new host of the late-night talk show.

And to celebrate the crooner’s first appearance on Fallon’s new gig, the two decided to unearth an old fave: their trusty “History of Rap” sketch, from Fallon’s Late Night stint.

For Friday’s big blowout, the two unveiled their fifth installment in the ongoing series, spitting out verses from hits by the Beastie Boys, LL Cool J, Kris Kross, Salt-n-Pepa, DJ Jazzy Jeff & the Fresh Prince, Outkast, Tone Loc and Run DMC, among others.

It was an appropriate closer to Fallon’s first week on the job, which saw a bevy of stars and luminaries – including Lady Gaga, Michelle Obama, Kim Kardashian and Lindsay Lohan – stop by to wish Fallon a bon voyage on his new gig.

Oh, and Fallon also ended his week a few pennies richer (big-ups, Stephen Colbert!).