The pair unpack "Joy to the World," including the cultural reference they couldn't ignore. "It's a piece of our history now," says Moffat.

The TARDIS is as much a part of Christmas as turkey, mince pies, and mulled wine, and former "Doctor Who" showrunner Steven Moffat certainly knows his way around a festive adventure. This year's holiday offering, "Joy to the World", is the writer's ninth, and it comes with all the trimmings you'd expect.

Filming that scene in the room that’s from millions of years ago was Coughlan’s favorite, she tells TV Insider. “It had a little bit of everything. You got that emotional moment and then you have the dinosaur and the escape, and I loved all of that,” she shares. “It’s such a fond memory.”