A marathon of all 12 episodes of Season 8, the most recent season of Doctor Who, is shown on BBC America today, beginning at 8 a.m. ET. That’s the season that introduced Peter Capaldi as the current and Twelfth Doctor – and the marathon serves as an all-day warm-up, and primer, for tonight’s all-new 2014 Doctor Who Christmas special, Last Christmas. Nick Frost from Shaun of the Dead plays Santa Claus, in an episode that also prominently features Jenna Coleman as Clara, my all-time favorite Doctor’s companion, in what may or may not be her farewell appearance. (No matter what happens, given this show’s time-shifting tendencies, I’m betting it’s not.) But beware: If you’re looking for a warm and funny Christmas TV treat, these Doctor Who holiday specials tend to serve up the scary and dark along with the froth and the fun.