Doesn't Buffy come with subtitles or something?
For example in the UK when one watches TV one can turn on subtitles. What's spoken is at the same time written as text on screen. Very helpful to connect the spoken sentence to the written word.
Or, in Holland most English shows are left in English and there are Dutch subtitles. Not as good a learning tool as the UK's one but still useful to connect the meaning to the spoken sentence.
In Japan I heard that most English movies are subtitled rather than dubbed. You have there an invaluable tool to learn the foreign language. Even if you don't pay attention there is a learning process at work here. I have been watching anime subtitled since two years and there are a lot of words and sentences that I have memorized thanks to that.