Justin Timberlake is spending the entire week on Late Night with Jimmy Fallon to promote his new album The 20/20 Experience and yet the most exciting moment so far has been all about nostalgia (to be fair, it's only Wednesday). Last night, Justin, alongside Jimmy and four of the show's writers (a.k.a The Ragtime Gals), performed a barbershop quintet version of the Timberlake classic "SexyBack." Did I mention that it will charm the pants off you? Oh, yeah. Say goodbye to your pants.