Neil Patrick Harris is to join the cast of Doctor Who for the show's 60th anniversary.
The Emmy and Tony-winning actor and comedian is currently filming scenes that are set to air in 2023.
Doctor Who showrunner Russell T Davies said: "It’s my huge honour to open our studio doors for the mighty Neil Patrick Harris… but who, why, what is he playing? You’ll just have to wait.
"But I promise you, the stuff we’re shooting now is off the scale. Doctor beware!”
The news follows previous announcements including the return of David Tennant and Catherine Tate.
One of the most loved pairings in Doctor Who’s history will reunite - although the BBC are being coy with exact details about how the duo will make their return .
A teaser reads: "The Doctor and Donna parted ways when the Doctor had to wipe Donna's memory, making her forget him, in order to save her life.
"He left her family with a warning: if ever she remembers, she will die. But with the two coming face to face once more, the big question is, just what brings the Doctor and Donna back together?
"In his last ever episode, David’s critically acclaimed portrayal of the Doctor famously said 'I don’t want to go…' Well it seems he - and fans across the globe - have got what they wanted as the iconic duo are on their way back…"
It was recently confirmed that Sex Education star Ncuti Gatwa is to become the new Doctor.
He will be taking over from Jodie Whittaker who will bow out with her final episode airing later this autumn.
Ncuti said: "This role and show means so much to so many around the world, including myself, and each one of my incredibly talented predecessors has handled that unique responsibility and privilege with the utmost care. I will endeavour my utmost to do the same."
Joining Ncuti on the new cast will be Heartstopper star Yasmin Finney.
Yasmin said: "If anyone would have told 8 year old Yasmin that one day she’d be part of this iconic show, I would have never in a million years believed them.