New Doctor Who Christmas Special Video: Two Time Lords in a TARDIS!

Even one of the most famous names in all of sci-fi is susceptible to slipping every once in a while.

So in this new footage from Doctor Who‘s upcoming Christmas special, when Peter Capaldi’s Time Lord accidentally informs a bewildered soldier (played by Sherlock‘s Mark Gatiss) that he’s been fighting in World War I, the man can’t quite believe what he hears.

“Yes, but, what do you mean, ‘[World War] I,” the man asks.

“Oh, sorry,” the Doctor responds. “Spoilers.”

The special, titled “Twice Upon a Time,” also features Capaldi’s Twelfth Doctor somehow crossing paths with the First Doctor, played by Game of Thrones’ David Bradley… who has strong feelings about the physical state of his just-met counterpart.

Not shown in the clip: Pearl Mackie, who — despite her apparent fate in the season finale — will appear in the special as the Doctor’s trusty companion Bill.

The special — Capaldi’s last before Jodie Whittaker takes over as the Thirteenth Doctor in Season 11—  is scheduled to air on BBC America on or around Monday, Dec. 25.

Press PLAY on the video above, then hit the comments with your timey-wimey thoughts.