As part of a statement on Harris' casting, Davies said: "I promise you, the stuff we’re shooting now is off the scale. Doctor beware!"
This latest statement certainly lines up with previous ones Davies has made on his plans for next year's 60th anniversary celebrations. He previously said that David Tennant's returning Doctor and Catherine Tate's Donna will face "the battle of a lifetime", while he's also teased that the team has "immense plans" for Nctui Gatwa's new Doctor.
Meanwhile, Davies also gave us more details on Harris' role in a post on Instagram, saying: "Neil Patrick Harris, welcome to Cardiff! Playing the greatest enemy the Doctor has ever faced. Such a great actor, such a great man, it’s an honour and a hoot. Have fun!"
Harris also played up his villainous role in his own Instagram post, including an image of himself in costume alongside the message: "My current gig. Never looked more dashing. Thank you for inviting me into your Whoniverse, @russelltdavies63. I’ll try my hardest to do my worst."
He continued: "This Doctor has no idea what’s in store. And even if he does… Who cares? Ha ha ha HA ha-ha-ha!"
Fans have already been fervently speculating about who Harris could be playing, if he is indeed playing a returning character. Previous villains already thrown into the mix by fans on Twitter include the Master, the Rani and a villainous version of the Doctor himself, the Valeyard.
One name which has perhaps been mentioned more than any other is the Celestial Toymaker, a First Doctor villain introduced in 1966, with fans pointing to the character's apron as seen in the first look image.
Just who Harris is playing remains to be seen, but one former villain has already been getting in on the fun, questioning Davies' assertion that he will be the "greatest enemy the Doctor has ever faced".
John Simm (Grace), who played the Master between 2007 and 2010, and then again in 2017, commented on Davies' post with the simple message: "Ever?!"
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