Nick Frost's first major movie role was as the amiable stoner Ed in the now-classic zombie romcom Shaun of the Dead, but he's also starred in his very own BBC sci-fi series, Hyperdrive, as Commander Henderson. What better training could you get for the role of a Doctor Who companion? Nick is no stranger to Doctor Who, either, as he'll appear (or has appeared, depending on when you're reading this!) in the 2014 Christmas Special as Santa Claus, but his low-key comedic sensibility would be a perfect foil for the crotchety and flinty Twelfth Doctor. What's more, the sight of the short and stocky Nick Frost alongside the tall and gaunt Capaldi would give the show a sort of Abbott and Costello vibe, something the Doctor/companion dynamic has never quite attempted before.