It sounds like Doctor Who fans are in for quite the adventure with this year's Christmas special.
According to the showrunner, fans can expect a breathtaking performance from Game of Thrones and Harry Potter alum David Bradley, who portrays the very first Doctor.
"We're still working on..." Moffat revealed, "the Christmas special, where David Bradley returns as the First Doctor. He exquisitely recreates William Hartnell's wonderful performance from all those years ago. A recreation of such beauty and precision."
Moffat also teased Peter Capaldi's role in 'Twice Upon a Time', which will conclude his arc as the Twelfth Doctor.
"And of course you've got Peter Capaldi in his very last go as the Doctor." Moffat explained. "He's going to break your heart! Your heart is going to be in pieces by the end of this."
But Moffat promises that it won't be all doom and gloom - particularly thanks to the first scene of the Thirteenth Doctor, Jodie Whittaker.
"Only Jodie Whittaker will be able to cheer you up again."
Moffat has had quite a bit of praise for Whittaker's first turn as the Doctor, saying that it marks the dawn of a new era for Doctor Who.
"I've seen Jodie's first scene as the Doctor," Moffat revealed, "and trust me we are in for a thrill ride. She is already brilliant. In such a tiny moment, she's given us the Doctor we've always known, but in, to say the least, a new way. We are in for a very exciting run."
Fans will have to see how all of those elements come together when the Doctor Who Christmas Special airs on Christmas Day, Dec. 25, 2017.