Even though they had just finished filming the Christmas special “Twice Upon a Time,” Doctor Who brought a small glimpse of it to Comic-Con—along with the news that Pearl Mackie would return as Bill, as well as frequent Moffat collaborator Mark Gatiss.
Steven Moffat, in what will be his last Doctor Who Comic-Con as a the showrunner, said that the episode is about both the First and Twelfth Doctors refusing to regenerate, and going on an adventure with Gatiss’s unknown character which the press release says is only known as “the Captain.” (Although he looks a lot like the classic fan-favorite Brigadier Alistair Gordon Lethbridge-Stewart, he isn’t, which you can tell because he’s wearing a uniform from World War I. But maybe he’s a relation and that’s why we don’t have a name?)
David Bradley’s first line as the Doctor in this footage—which also has original First Doctor William Hartnell’s performance from decades ago merged into his—are his lines to Cybermen from “The Tenth Planet,” the story in which he regenerated, which tells us exactly where in the timeline the Twelfth Doctor is meeting his first incarnation.
All of this was a goodbye to Moffat and Peter Capaldi, also in his last Hall H appearance as the current doctor, and even Mackie, who confirmed that this will be Bill’s last outing.