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They began with Run-DMC's 1985 classic 'King of Rock' and quickly segued into LL Cool J's 'Mama Said Knock You Out.' Timberlake did a first-rate Will Smith impression on the next track, 'Parents Just Don't Understand,' and then the Roots -- Fallon's ace backing band -- stole the spotlight on De La Soul's 'Me Myself and I.'
Moving into the early '90s, Timberlake and Fallon big-upped rumps on Sir Mix-A-Lot's 'Baby Got Back' and worked in some Michael Jackson-style vocals on the hook from Young MC's 1989 hit 'Bust a Move.'
Before closing with several more recent tunes -- including Kanye West's 'Stronger' and Nicki Minaj's 'Super Bass' -- and a reprise of 'King of Rock,' the pair hit its peak with Ice Cube's 'It Was a Good Day.' When Fallon rapped the line about not having to use his AK, Timberlake shot the host an incredulous look.
"You don't have an AK, do you, Jimmy?" he asked, prompting the comedian to admit that he does not, in fact, own an AK-47 machine gun.
Watch 'Rewind: Fallon Before Late Night'