You know that the werewolves versus vampires film Underworld has spawned three sequels, with a fourth, Underworld: Blood Wars, coming soon. But did you know that when director Len Wiseman was developing the first Underworld, he got too ambitious with his story? Eventually he realized that his screenplay was getting to dense for one film. Rather than condensing everything to fit into a single movie, he removed whole sections so that they could be used for future sequels. That’s just one of the blood-sucking facts featured in this new episode of You Think You Know Movies!