Toby Whithouse wanted to emphasise the amount of danger The Doctor puts people in, which is pointed out by Rory in the episode. He believed that the companions over time developed the same mentality as The Doctor in running towards the danger, and so Rory was a great opportunity to question that.
Helen McCrory's costume was designed to be similar to her alien creature to make the transition smooth. McCrory was coached to move like a fish, which she pursued diligently.
Each pair of teeth for the vampires was unique and moulded to their mouths. They were hard to speak with and Alex Price's lines were re-voiced, though he commented he got "quite good" at speaking with them.
This episode was filmed in Trogir, Croatia.