In the long-running BBC show Doctor Who, our eponymous hero flits around time and space curtailing the spread of evil, defending the human race, and according to the first trailer for "The Snowmen," prevents all the children in the world from ever having bad dreams. But it seems as if he won't be living up to his responsibilities in the latter task, because if the trailer is anything to go by, some children who watch this are in danger of having nightmares.