What if he had gotten Vincent Price instead?
At one point, while trying to persuade Orlok to put off retirement and make his next picture, Sammy says in disgust something like "Forget it, I'll get Vincent Price instead."
Not to take anything away from Boris Karloff, who is excellent here, but what if Bogdanovich had gotten Vincent Price to play the part of Orlok. Of course, the film might not have been made at all without Karloff, because using him was part of the deal with Roger Corman. But in some ways, the part would be more suitable for Price. Vincent was, after all, AIP's resident horror star and his roles as often as not had him playing insane men who turn into serial killers of sorts in all those Poe adaptation. That would provide a nice ironic parallel to Bobby's actions.
On the other hand, part of Karloff's power here is that he seems so frail, even as he stands up to those around him. Price was in his prime at the time and might have come off as too robust.
Anyway, it is something to think about. Is Karloff just so perfect in the role that someone else couldn't have done it as well. Like Price? Or Christopher Lee? Or Peter Cushing?
And if they did a remake, who today would be an equivalent to Karloff?