"The Zeppo" is kind of a meta-episode focused on the "useless" character of the show, Xander. Everyone has a function or power they serve in the Scooby Gang except for him (one's a witch, two are slayers, one's a vampire, one's a werewolf, one's the supernatural expert), and his bitter ex, whom he's still in love with, cruelly points that fact out to him at the beginning episode, essentially shattering him. It's an episode in which the Gang faces their ~Most Horrific Apocalypse Ever~...yet we don't actually see it because we stay with Xander the whole time, and they just want him to stay on the sidelines where he'll be out of danger.
So instead, we just get glimpses of all this world-ending melodrama in the periphery, whenever Xander kind of awkwardly walks in on it - kinda like if someone walks in on a dramatic episode of Buffy completely out of context - and it's hilarious. Meanwhile, making his best attempt to stay out of trouble, Xander finds himself getting roped into a night of "fun" with a gang of juvenile delinquents who turn out to have been recently-risen-from-the-dead and planning to blow up the school. Xander figures out their plot, chases them down, defeats them all and stops the bomb from going off at the last second. All of this remains unknown to everyone else on the show, as all of his friends were too busy saving the world to notice. And Xander doesn't even bother telling them, having finally, quietly, regained his bravery/confidence, as he happily listens to their war stories of the night before and how they just barely survived "The Big One."
My description can't possibly do it justice, but the way the micro and macro storylines intersect is almost always awesome and hilarious, and the whole episode is pretty much a work of genius. It's the perfect example of how to highlight "the little guy," imo. So if this series could mirror any episode of any show Joss has ever created, I'm SO glad it's this one.
