Inspiration for this post came while watching Vincent Cassel in Brotherhood of the Wolf.
You should recognize him from Black Swan. In both films he does creepy-sexy very well. In Brotherhood of the Wolf his character comes off as a tragic figure at first. Lost of an arm in an hunting accident, and his sulking in the background, might make some watchers of the movie, wonder who this is. When it's revealed. SPOIlER: When he rapes and tries to kill his sister. He crosses the line completely into creepy.
Vampires (you knew I would come back to them) are the perfect mix of Creepy Sexy. My first brush with that was in the film Fright Night.
Why is there a connection between the two?
You get the same physical reactions to arousal as you do with fear. All due to a lovely little hormone call Epinephrine or you might know as adrenaline. That hormone knows we have to get our bodies ready. In the case of fear to "fight or flight" or in the other case, to make it more pleasurable. It increases our heart rates, makes out pupils bigger, makes the blood vessels larger, and weakens the immune system for a bit.
Vampires are one of the few monsters that can mix the creepy with the sexy very well. The other maybe werewolves. Although they are corpses, many of the old tales did remark on how well they looked. Yet, they are a predator, feeding on humans.
Let's say you find one coming toward you on the street. You're body knows, probably before you do, that this is trouble. The Epinephrine kicks in, getting you ready to flee or stay and fight. But you notice at the same time that person is pretty good looking. You are going to misinterpret your body's signals. You think you are attracted and the whole time your body is telling you to run.
It's that mix up of the signals that makes vampires so titillating. You should be repulsed and yet drawn to them. Because if you are not, they are just some creepy guy that likes blood.