The Christmas special may still be a few months away, and this year is certainly a bittersweet one, as it concludes Peter Capaldi's run as the Doctor making way for Jodie Whittaker to take the reins.

Outgoing showrunner Steven Moffat dropped a few hints about what fans can expect when the special airs in December. Moffat sent the show's colorist Stuart Humphreys a video message, with a sneak peek into the Christmas special. He revealed that they are still working on the episode and that fans can expect a wonderful performance from "Game of Thrones" and "Harry Potter" actor David Bradley, who will be portraying the First Doctor, originally played by William Hartnell.

Moffat continued to praise Bradley, saying that he did an excellent job in capturing Hartnell's performance during the show's very first years. He also added that this is Capaldi's last time as the Doctor, and that his last performance is definitely going to have fans reaching for tissues, much like the exits of his predecessors.

Yet, Moffat also gave fans a look into the bright side thanks to Whittaker's first scene as the Thirteenth Doctor, followed by praises of her performance. Moffat said that in one small scene, Whittaker has already captured the essence of the Doctor that everyone has known, and that fans will be in for an exciting ride ahead.

In keeping with the tradition of old companions showing up in some form or another, it might also be the case for Capaldi. Along with the return of Bill Potts (Pearl Mackie), Capaldi teased that Jenna Coleman, who played Clara Oswald, might be coming in as well. According to Radio Times, Coleman was approached to make a cameo, and during the San Francisco Comic-Con panel recently, Capaldi hinted that she may come back in time for his farewell.

A fan asked Capaldi during the "Doctor Who" panel at the event if fans will ever see Clara again, Capaldi only responded with "I think you may." After a moment, the outgoing Doctor added that he will see her again, and everyone else may see her again as well, but he will not reveal when.

Of course, he may only be referring to if Clara will ever come back in one way or another in the show regardless of who is the Doctor, but it is not too far-fetched to think that she will make an appearance in time for his farewell.

The "Doctor Who" Christmas special, "Twice Upon a Time" will air on Dec. 25.