thanks to scifiwire.com:

We don’t watch ABC’s romantic comedy detective series Castle, starring Nathan Fillion, though we’ve heard good things, but after watching the following promo, we give them high marks for sci-fi cred: Among other things, Fillion’s character dresses up for Halloween in a very familiar Browncoat and tight-pants outfit.

More here

That was hilarious, he knows really well his vampires and werewolves 😉 Will you watch this episode next Monday?