Neil Patrick Harris interrupted James Corden on The Late Late Show to challenge him to a Broadway riff-off.
"Your silly jokes can wait, Corden. We have a score to settle, and it's about Broadway."
"What do you want Neil?" James asked, "What you want is a Broadway musical Riff-off, is that what you want?" He continued.
And thus they proceeded to have an epic Broadway Riff-off where these two hilariously sang their hearts off to some Broadway classics.