Stephen Colbert to Sing Rebecca Black's 'Friday' on Jimmy Fallon's Show for Charity (Video)

Fallon tells viewers that if they raise $26,000 for, his "BFF for six months" will perform the song with his house band the Roots.

Want to hear Stephen Colbert sing Rebecca Black's "Friday"? Better open your wallet.

The Colbert Report host recently auctioned off a painting of himself for $26,000 to benefit charity and subsequently announced on his show that Jimmy Fallon, his "best friend of six friends," was planning to match the donation.

The only problem? Fallon hadn't actually said that.

On Tuesday's Late Night With Jimmy Fallon, Colbert made a surprise appearance to urge Fallon to donate to, which helps classrooms in need.

Ultimately, Fallon got back at Colbert with a "promise" of his own.

"If we can raise $26,000 by this Friday, I will promise that my BFF for six months, Stephen Colbert, will come on this show and sing Rebecca Black's 'Friday' with the Roots, and that is a promise that I am making from him to you," Fallon told viewers.

To donate, visit, which noted on its website that "this is not an April Fool's joke."