During the glory years of The Simpsons—either the first 10 seasons or seasons three through eight if you want to get picky—the show was groundbreaking, incomparably clever, and built on a foundation of unprecedented use of allusion. Bill Oakley, who wrote for the show for seasons four through six and produced it during seasons seven and eight, just penned a reflection for The Awl on how the impressive roster or writers crafted those classic episodes.
Here's a bit about the biannual writers' pitch retreats:
Many people were very, very intimidated by all this stuff and it was like the worst part of their year. But for us, it was our favorite part of the year. My writing partner Josh Weinstein and I would work really hard on these things and we'd usually have a couple of ideas stored up that we'd been working on for a couple months, and we just liked the opportunity to discuss them and have everybody there pitching in their jokes. And, you know, usually you would get laughs. And people would give suggestions like, oh, this could happen or that could happen, and you'd usually talk about the idea for about twenty minutes, with everybody pitching in stuff off the top of their head.
You wanted to have a story that had a beginning, middle, and end. You didn't necessarily have to have the act breaks, but you couldn't go into the retreats with just one sentence, you know, something like "Bart vs. Australia." These are busy, highly-paid people, and you didn't want to waste Jim Brooks' time with something half-assed. I'm pretty sure there was at least one guy who got canned after his crummy performance at the story retreat. So you wanted to be prepared, as your job was on the line to some extent. So you wanted to come in with a story that would take ten minutes to tell and would have the act breaks, or at least some semblance of the act breaks.
You can also read the second part of Oakley's essay here. It's part of The Awl's "Classic Simpsons Week" series, which offers a wonderful reprieve from whatever it is you're supposed to be doing at work right now.