Oz

The idea that a dopple ganger is really just another side to a person, and not necessarily their opposite is one of the things that I notice the most in this Buffy episode.

I think Joss Whedon found a brilliant way to introduce another side of Willow in this episode, that makes her later personality/character development even more believable.

However, the person that interests me the most is Oz. I don't know how many people noticed, but when vampire Willow gets back where she belongs, the person who pushes her onto the stake is Oz. So, given the episodes we've watched with Tara, I'm not giving anything away when I say Oz and Willow don't stay together.

The way Whedon uses Oz to kill Willow in the alternate reality shows that there are too many differences between the sides of their personalities that they don't always show. This emphasizes the idea that many of the Buffy characters have parts of themselves that are dark or evil.

... I sort of lost my train of thought...