Some are more surprising than others. Werewolves who can control themselves are as old as Bisclavret and use of silver and the effect of the moon on them are in fact Hollywood fare. Old time medieval vampires were not sexy -- think zombies from the movies. Dragons in eastern European fairy tales were not large, indeed I've read a collection where the translator left it as drakos on the sophisticated grounds that they were more like ogres anyway.
But you can't count on readers knowing that and the folklore might throw them out of the tale.