Watch: Stephen Colbert Sings "Friday" on Jimmy Fallon (Video)

Stephen Colbert, Jimmy Fallon

Watch Stephen Colbert sing “Friday,” that Rebecca Black hit, on Jimmy Fallon April 1 (video). Why is Stephen Colbert singing “Friday” anyway?

Seems Stephen Colbert volunteered Jimmy Fallon, his best friend for six months (see how that all came to be), to donate $26,000 to his Donors Choose charity. Fallon had no idea and Colbert appeared on Late Night with Jimmy Fallon to explain himself.

Since it’s a worthwhile charity, Jimmy Fallon asked viewers to donate – and if they reached the $26,000 goal, Stephen Colbert would sing Friday!

Naturally, Jimmy Fallon fans (Fal Pals or whatever they’re calling themselves) and Stephen’s Colbert Nation of devoted fans were more than happy to pony up the bucks to have Stephen Colbert sing Friday.

Jimmy Fallon tweeted: “Thank you, everyone!!! We did it!!! Stephen Colbert will (has to) sing “Friday” this Friday on our show!! Awesome!! #26000 #donorschoose”

Watch Stephen Colbert on Jimmy Fallon in the video, as well as on The Colbert Report, where he laments, “There is no way to learn those lyrics by… the last weekday… whatever it’s called.”