SEASON FINALE: In the U.K., this episode came months after the Season 2 finale, as a stand-alone holiday special that was televised on Christmas day. That’s why its title, “Comfort and Joy,” quotes from a familiar Christmas carol – and also why it includes a scene of merry holiday festivities. But it also includes an action sequence that I’ll call, though the episode does not, “Queen Victoria on ice.” Watch for it. Check local listings.