There had been whispers, rumors, even discussions about a Simpsons movie for a long time. As in, let's brainstorm over Crystal Pepsi long. The closest flirtation came in 1992, when Brooks wondered if the first cut of the ''Kamp Krusty'' episode could be expanded into a feature. But back in those early, heady days of the show — when bootleggers hawked Bart T-shirts on street corners — the staff was too busy churning out episodes to multitask multiplex-style.

That wasn't the only hurdle. Fox had long balked at Brooks' terms, which were: Commission us to write a script, but if we don't like the results, we don't have to make a movie. ''It was a tough point for them to swallow,'' admits the producer. ''But it was very necessary for us to feel secure as we moved forward. It was an odd contract dispute — we were arguing against a green light.'' However, Tom Rothman wanted that green light badly, so when the current chairman and CEO of Fox Filmed Entertainment became studio president back in 1999, he persuaded the powers that be to accept Brooks' conditions. ''Regardless of what it said on a piece of paper, if Jim Brooks and Matt Groening weren't happy with the movie,'' reasons Rothman, ''it wasn't a movie we should make.''

While the big screen loomed as the ultimate challenge — ''It's like Mount Everest,'' says Jean. ''You try to do it because you can'' — most at Simpsons HQ thought they'd strap on the crampons after TV's longest-running comedy was retired. But as it became apparent that the series wasn't going anywhere, ''we figured we'd better get started,'' quips Scully.

In 2001, the main voice actors signed a three-season extension with a film provision. Brooks thought it'd be ''romantic'' to reunite with early-days Simpsons players, so he and Groening slowly assembled an all-star team. Veteran series director David Silverman was hired to helm. (He'd left Pixar in anticipation of the gig. ''Steve Jobs said if it'd been for any other reason, he would've been very upset with me,'' he recalls.) Longtime showrunner Scully and current showrunner Jean were tapped to produce. The latter must mainline Buzz Cola: Jean oversaw the writers' room while continuing episodic duties. The room was filled with ex-exec producers and scribes. (For you hardcores, that list included George Meyer, John Schwartzwelder, John Vitti, David Mirkin, and Mike Reiss; Ian Maxtone-Graham and Matt Selman joined in later.) Two high-profile yet not surprising exclusions: Sam Simon, who'd codeveloped the series with Groening and Brooks but left over creative differences in 1993; and writer-producer-turned-late-night-star Conan O'Brien, who Jean says would've ''laughed'' off an invite. ''That makes no sense,'' responds O'Brien. ''I cleared my talk-show schedule for a year at great financial cost to myself, got an apartment right outside the Fox lot, and told them I was ready to report to work. All I heard back was that they were having trouble finding me a parking space, and then they stopped returning my calls altogether. I am stunned and disappointed.''

When Springfield's finest gathered in 2003, they were well aware of the challenges — and skepticism — ahead. ''The idea of doing a movie spin-off from a TV show smells bad, y'know?'' says Groening. ''South Park was proof that you could do something really funny and different from the show. If you weren't familiar with South Park, it was a great movie, and if you knew it, then it was even better.'' There was also that weensy issue of digging up a fresh plot. Says Scully: ''Story-wise, character-wise, joke-wise...after 400 episodes, we feel like not only have we done it all, we've done it all three times, and the audience has been very kind not to notice.''

NEXT PAGE: ''The carpet is covered with stains of sitcoms past, and I think the Pauly Shore show was written in this room.''