this might be my favourite
According to an article I just read, Stephen Colbert did this because Jimmy Fallon told him that he would donate $26,000 of his own money to a charity of Colbert's choice if the latter sang Friday on his show.
Basically... yes... I watch Colbert's show regularly, and it was a little more elaborate than that but I believe the money raised went to classroom supplies for needy schools. Great cause, IMO.
Fallon on Colbert's show a few weeks ago arguing about who has the better Ben & Jerry's ice cream flavor before tripping out on ice cream headaches and breaking into song was pretty funny too.