Spike mentions that he had met Dracula before and that "the poncy bugger owes [him] £11." In a comic book entitled "Spike vs. Dracula", when Bram Stoker's book was first published in 1897, Spike bought a copy for Drusilla, which Dracula himself destroyed. The book cost Spike £11.
The vampire who was going to show Buffy a darker side of herself was originally envisioned as "just another vampire who rode a horse and was all cool", says writer Marti Noxon. "I kept saying, 'Like Dracula'" - until Joss Whedon said, "Why not Dracula? He's public domain."
Dracula says to Buffy, "you think you know what you are, what is to come. You haven't even begun." Tara says this to Buffy in the season 4 finale during her dream sequence.