Spoiler alert! Michelle Gomez's renegade Time Lady Missy is going to regenerate into James Corden... or maybe he's just dressed up as Mary Poppins for a sketch on his chat show...
Either way, Gomez would be down with it if it did happen.
Of course, this could potentially complicate Doctor Who canon, since Corden played the Eleventh Doctor's landlord Craig in 2010 episode The Lodger and its sequel Closing Time.
And if it turns out Craig is not actually an ordinary human but instead the next incarnation of the Master after Missy, that would raises some serious questions about timelines and exactly what the Master was up to when he was pretending to be a hapless dad. Or maybe there was a Chameleon Arch involved and he was actually unaware of his true identity. It wouldn't be the first time...
Perhaps this is Doctor Who showrunner Steven Moffat's final flourish before he signs off at the end of the year.
Or perhaps it's just James Corden dressed as Mary Poppins.