Television Without Pity’s list of the worst episodes of great TV shows (by which they mean “shows that have been on in the last 10 years) is a bit heavy on episodes with plot elements they don’t like, as opposed to genuinely terrible episodes. For example, it is tempting to pick “Where the Wild Things Are” as the worst episode of Buffy the Vampire Slayer because the basic story hook is not only stupid, but kind of stomach-churningly disgusting. (And by that I mean, of course, sex with Riley. Between that and the many giant phallic snakes on the show, I think the snakes are far less horrifying.) But it’s not really a badly-executed episode: it aims to be cheesy with a heavy-handed metaphor, much like some of the sillier season 1 episodes, and it does what it intends to do; I like the fourth season of Buffy because it was the last season to be unashamed of the cheese factor. Whereas a much worse episode, like “Wrecked,” actually wants to be serious and moving, and fails completely. I think there’s sometimes a tendency to pick as the “worst” episode one that has a particularly loathsome or upsetting plot hook, like Michael Scott trying to frame Toby, as opposed to episodes that are just badly done.
As Myles McNutt pointed out on Twitter, “short-term memory” plays a part in this as well, because we sometimes tend to pick the worst recent episode, as opposed to the early episodes that were worse. 30 Rock‘s uneven early episodes had many worse efforts than this season’s Night Court episode. (But you could argue that a show should be given a pass for mistakes it makes when it’s still trying to find its voice, whereas there’s no excuse for turning out a poor episode once the show is in its prime; that’s why, say, a bad recent episode of The Simpsons is more annoying than a bad episode from the first batch of 13.)