From Slate:
Whether we’re living in the age of Peak TV or Trough TV, one thing is clear: There’s too much TV. Thankfully, not every show has to be watched in its entirety. One of the best things about television is its serialized nature, the continuous thread that strings viewers along from one episode to the next. It’s a cliché that prestige television is the new novel precisely because of the way that many dramas develop their characters and plots over many hours of storytelling. But an older virtue of TV is its brevity—the way a scenario can be introduced and resolved within the space of an hour, or half that—and some of the best episodes are less like chapters in a long-running novel than like short stories or short films. These are stand-alone episodes.
What makes a stand-alone? There’s been no shortage of debate about this question, but for our purposes, we’re defining it simply as an episode that stands up on its own, whether or not you’ve seen the rest of the show. Some are “bottle episodes,” which typically confine a small cast to one location to save money. Some are “departure episodes,” in which a show abandons its usual format or style to suddenly become, say, silent, animated, a musical, or about a minor character it was never about before. But not all bottle episodes and departure episodes are stand-alones, and vice versa. It’s for this reason that you won’t find Breaking Bad’s celebrated “Fly” on this list: It may be a bottle episode, but it doesn’t stand alone, because the best thing about it—how the housefly is a metaphor for everything else going on in the series—is comprehensible only to those who have watched the show.
More here.