Question: My old Smurf t-shirt doesn't fit me anymore. I'll send it to you in exchange for some Supernatural prattle!
Answer: You got a deal! I just found out that Buffy's Amber Benson will guest star in the episode Bloodlust. She plays get this a vampire(!) who kidnaps Sam, but then delivers some very surprising news that causes the Winchesters to rethink their stand on the supernatural.