It’s in the final episode, actually.
The entire episode of Buffy vs. Dracula counts as a pop-culture reference, I presume. Pretty much every scene was a shout-out to some part of the Dracula pop-culture-folk-lore or another, right down to Spike calling the Count an attention-whore and claiming that his book was the reason that every random guy on the street knows at least in theory how to kill a vampire.