Christmas is a time for presents under the tree, songs... And saying goodbye to Peter Capaldi, as the veteran actor leaves his role as the lead on Doctor Who after three seasons in the upcoming Christmas Special. It's also a goodbye for longtime showrunner Steven Moffat — and possibly cast-members Pearl Mackie, Michelle Gomez and Matt Lucas, who seemed to finish their arcs in the season finale, but have teased that one — or all of them — may be back.

And if that wasn't enough, David Bradley (Game of Thrones) joins the cast playing the very first Doctor, originally played by William Hartnell. In a neat meta-twist, Bradley originally played Hartnell in a biopic of the making of the first episode of Who, An Adventure in Space and Time. Wibbly-wobbly, timey-wimey indeed.

During the Christmas Special, The Doctor will regenerate — meaning change his face and body after a near death experience — into the new Doctor, played by Jodie Whittaker.

So were the fans who packed the 6,000-plus capacity Hall H to see the Doctor Who cast at San Diego Comic-Con flippin' excited to see the first scenes from the episode? You bet they were.

It starts with a shot of the original Doctor, fading into color as he morphs into David Bradley. Over older scenes, titles flash: "One Man. One Destiny. Twice."

The concept? They're trapped in a single moment, teamed up with Mark Gatiss' soldier who joins them on their adventure.

And... Bill is back! Pearl Mackie returns in the special, which is called "Twice Upon a Time."

Watch it here:

The Doctor Who Christmas Special airs, you know, on Christmas, on BBC America.