Stephen Colbert and Jimmy Fallon got together four weeks ago and sang about their shared elitist status as people with their own Ben & Jerry's ice cream flavors. Their duet ended with an arrangement to become Best Friends For Six Months.

Since then, Colbert raised money by auctioning off one of his paintings, and then jokingly roped Fallon into charitably giving, too — except Fallon then countered by daring Colbert to sing a cover of Rebecca Black's "Friday" on Late Night with Jimmy Fallon tonight.

Before this happens on TV, though, Colbert and Fallon got on the phone with Arianna Huffington to explain what it's like to be TV BFFSMs.


Where does this leave Craig Ferguson, though?

Ferguson and Fallon seemingly had their own TV BFF relationship going on to contrast themselves with the "late-night wars."