How the hell did NBC not pick this up?
THR explains (http://www.hollywoodreporter.com/news/how-nbc-passed-jimmy-fallons-786992). Basically, NBC felt it was "too small," and the original pitch was made before the Emma Stone clip from Tonight went uber-viral.
And part of the key is, as Vulture acknowledges: based on the behind-the-camera talent, they did land Actual Stars for this, not (apologized to Watts) Dancing With The-level personalities.
They front-loaded the bigger names, looks like--this week is Mike Tyson/Terry Crews, next week is Hoda Kotb/Michael Strahan, and we have Derek Hough/Julianne Hough in our future.