Justin Timberlake Waits for the Beep With Jimmy Fallon During Hip-Hoppin' Segment

New "Tonight Show" host Jimmy Fallon has been celebrating his inaugural week in the gig by providing viewers with the fifth installment of his famous/extensive "History of Rap" series. The talk-show host took full advantage of his musical guest, Justin Timberlake, on Friday to show off some little-known highlights from the hip-hop playbook, but the pair really hit an apex when they pulled out a gem that only those of, ahem, a certain age will recognize.

If you remember the '80s, you'll no doubt remember when people had, like, answering machines for their phones. The big clunky standalone kind. Right?

If you're still with us here, you'll probably know what Fallon and Timberlake are talking about when they rap these words: Wait for the beep.

Yup, the pair are referencing "Crazy Calls," that infamous infomercial that offered a cassette providing the "gift of gab for your answering machine." In addition to the rap, there's a version of Beethoven's Fifth, the Andrews Sisters, and five other soooo-clever messages on a convenient cassette tape. Only $14.95, dude!

If you're too young to clearly remember a time when people didn't have mobile devices (Timberlake and Fallon are both under 40, so they may semi-qualify), or simply need a refresher, check it out:

In addition to waiting for the beep, Fallon and Timberlake rounded out their latest installment of their History of Rap series with inclusions of songs by N.W.A., Tone Loc, Kriss Kross, Run-DMC, Positive K, Jay Z, Skee-Lo...oh, and the theme song to "The Fresh Prince of Bel-Air."

Is there a hip-hop classic these two have not hit yet? Well, after hearing "Wait For The Beep," we are pretty sure the pair have exhausted the genre!