'Carpool Karaoke' behind-the-scenes doc reveals how it almost never happened

The Late Late Show may be finished, but Carpool Karaoke has long since cemented its place in internet history.As we learn in the behind-the-scenes mini-doc shared on The Late Late Show's YouTube channel, though, getting it off the ground was no easy feat. In the clip above, James Corden and various members of the staff who worked on Carpool discuss how the idea came about, how they initially struggled to find anyone to do it ("Everybody said no," says executive producer Rob Crabbe), and how the whole thing snowballed into the viral mega-hit it is today.One moment at the end that provides a glimmer of hope for Carpool fans?"We could never have expected it to be what it was, and we still love making them," says executive producer Ben Winston. "And I hope, maybe we can continue making them even after this show's done. I don't know."