Mike Scully, one of the founding fathers of the ever-popular television show “The Simpsons” and one of the lead writers and producers of the forthcoming “The Simpsons Movie,” is recalling the unlikely evolution of Springfield, the fictional town where both are set. But first, he has to apologize — or take credit — for the television rules that applied in my house when I was growing up.

“What you said about your mom not letting you watch the show, I dealt with a lot of that,” he said in an interview Friday. “There were kids who weren’t allowed to come over to my house and play with my kids because their parents knew that I wrote the show. Of course, if kids did come over, the first thing they’d ask is if they could watch the show, and so I watched it with them.”

Anyone who was between the ages of seven and 17 in 1989 likely remembers clandestinely tuning in to the new cartoon on Fox. It was crudely drawn and somewhat crass, which made it exciting and dangerous. Then there were those schoolmates whose parents were hip enough to buy them T-shirts with Bart Simpson and “Eat My Shorts” emblazoned across the front. Who could have imagined that nearly 20 years later, that yellow, spiky-haired brat would be a cultural touchstone for a generation of 21st-century Americans?

“It’s been an odd journey as we went from being this show that parents didn’t want kids to watch to being the show that parents watched with their kids,” Mr. Scully said. “I think that’s why Bart was such a major character in the beginning, and as more parents started watching, Homer really emerged as the more prominent character.”

Indeed, as the program has swung from the fringes of acceptable programming on a new and fledgling network to one of the world’s most recognizable global brands (and from the child’s perspective to the parent’s), with episodes airing several times a day on multiple networks across the globe, so has the possibility, even this many years later, of a feature-film treatment.

Of course, in other ways, the passing of the years has gradually made a major “Simpsons” rebirth less likely. Today’s television dial is crammed with animated series that simply would not exist were it not for “The Simpsons” and the ground it broke — from “South Park” to “King of the Hill” to “The Family Guy.” But those shows, which were created by “Simpsons” devotees, have, according to many viewers, surpassed the original in terms of the modern TV comedy it pioneered. This is why longtime “Simpsons” fans were as unsure about the prospects of a full-length feature as the show’s creators.

“Everyone agreed, when talk of a movie would come up, that we should wait until the series was done before tackling a movie,” Mr. Scully said. “To do both at the same time would be too much work, and each would suffer as a result. But then the show just kept going year after year, and you reach a point when you realize: If we don’t start doing this soon, we’re going to be too old to write it.”

So it was in 2003, when the first of about 75 scripts was completed, that the genesis of a “Simpsons” feature was conceived. But the real work was just beginning. Mr. Scully and company would ultimately spend the next four years tweaking and trimming in search of that perfect pitch and tone, that right mix of inside jokes for the diehards and universal jokes for the newcomers.

“Initially there was more inside stuff for the die-hard, obsessive fan,” Mr. Scully said. “But what we found as we took the film out to test screenings was that audiences didn’t know some of the supporting characters as well as we were expecting them to. When Nelson [the schoolyard bully] comes onscreen, or if they see Milhouse [Bart’s best friend], we thought they were going to go nuts, but what we found is that they didn’t do anything. So we realized fairly early on that we couldn’t count on any of the show’s dynamics to carry the movie.”

And it wasn’t just newcomers to the series who required the writers to tinker and broaden the story. Mr. Scully explained that some of those test audiences who didn’t recall Nelson or Milhouse were some of the same watchers who helped build “The Simpsons” into an iconic franchise.

“A lot of people were fans of the show, but hadn’t watched in 10 years or so,” he said. “They still considered themselves fans, but things do get forgotten over time, and we realized we couldn’t count on people remembering every little detail or minor character.”

So from draft to draft, these inside winks were cut down and eliminated, though Mr. Scully said he expects many will be reinserted for the eventual DVD release of “The Simpsons Movie,” which should hit stores in time for the holiday season.

As it stands now, the movie’s script focuses far more on the Simpson family than the wider Springfield universe, limiting the number of side characters and random tangents for which the show has always been famous. In fact, a healthy portion of the film removes the Simpson family from the insulated haven of Springfield altogether when an environmental disaster forces them to flee to Alaska and leave the familiar churches, taverns, Kwik-E-Marts, and nuclear power plants behind.

The million-dollar question this week for Mr. Scully and his creative team — as well as for the marketing executives at 20th Century Fox and the industry watchers — is how a big-screen “Simpsons” will fare, not just 18 years after it burst into the public consciousness, but as it goes head-to-head with the likes of Harry Potter and Jason Bourne. Chad Hartigan, a box-office analyst with Exhibition Relations, said he’s encountered many of the same conflicting signals that Mr. Scully faced in writing and then re-writing the film.

“It’s a really unique case,” he said. “‘The Simpsons’ has some of the criteria of a big summer movie — a name brand, an established fan base — but the reaction to the trailers has been very mixed. Why go out and pay for something you can see for free on TV? And why go back to a series you stopped being a fan of a decade ago? Is this really appealing to anyone who’s not a hard-core fan of the show? If only the current audience of the series shows up, that won’t be enough.”

Mr. Scully says the final product will speak for itself. “We’ve worked hard to deliver a good story that stands on its own, but we’ve also worked hard to layer in some surprises. In the crowd scenes, look for all the extra hidden faces in the background, and for the fans, I think there are a few shots that people might not catch right away, particularly in the end sequence with Springfield gorge and a hilarious tribute to one of the classic episodes from early on.”

Fans of “The Simpsons” will no doubt get the reference. Whether they’ll consider it worth their $11 is another story.