Fallon: Colbert Will Sing Rebecca Black's 'Friday' With The Roots For $26,000 (VIDEO)

When Stephen Colbert auctioned off his portrait for Donor's Choose charity for $26,000, he was delighted to announce that Jimmy Fallon would be matching that amount in a donation of his own. Only problem was, Colbert made the promise without telling Jimmy.

And why shouldn't he have? He and Jimmy are Best Friends For Six Months (BFFSMs).

That is the newest chapter in the Colbert/Fallon bromance fable that has been playing out across late night screens for the last few weeks. It's been a genuine delight to see the cross promotion between the shows in the service of charity, but Fallon kicked it up a notch last night. After a broken-hearted Colbert left the stage telling Jimmy to consider what he had lost, Jimmy issued a brand new (unapproved by Stephen) challenge: if Fallon's audience can raise $26,000 for the charity, Stephen will return to "Late Night" and sing a rendition of Rebecca Black's "Friday" accompanied by The Roots.

Finally, we find the real reason that horrible song exists.

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