The genesis of “Simpsons World” — the authenticated app that is the multimedia playground for all things connected to the iconic toon — was a deal point in the megabucks syndication deal that brought “The Simpsons” to reruns to FXX.

As FX Networks and Fox’s Twentieth Television were hashing out the transaction in the early fall of 2013, it became clear that FX would need expansive streaming rights to the 550-plus episodes to make the deal, with an estimated pricetag of $750 million, financially viable.

Throughout the sale process, Twentieth TV kept close counsel with James L. Brooks, Matt Groening and the other pillars of “The Simpsons.” Twentieth’s Steve MacDonald, FX’s Chuck Saftler and other other execs handling the deal wanted to make sure the creative stewards of the franchise were comfortable with the sale that made “Simpsons” reruns available on cable for the first time.

When it came to the details of making “Simpsons” episodes available via on-demand streaming, Brooks was initially hesistant out of concern for diluting the show’s value over the long term.

“I’m always a little nervous about ubiquity,” Brooks told Variety.

Eventually, Brooks agreed to the SVOD rights plan with one big stipulation: The show could not be warehoused on a bland site with long list of episodic titles. If “Simpsons” was going to be out there for fans to access 24/7, the environment had to be something special. It had to push the envelope on interactivity and creativity. It could not be boring.

Nearly one year and many meetings later, “Simpsons World” has greatly exceeded the expectations of Brooks’ and the team of “Simpsons” writers and creatives who helped craft the app, which launches Oct. 21 as part of the FXNow authenticated streaming serivce.

The app launch aims to continue the momentum that “Simpsons” garnered with the headline-making 12-day, 25-season marathon that heralded the show’s cable launch on FXX in August.

The most gratifying aspect of “The Simpsons” migration to cable and the app is that the entire marketing effort became a “true partnership” of the series’ writers and the FX team, according to Brooks. The most exciting part, he added, is that the app will continue to evolve and add new features — including original content.

“We’re a show that lives to be edgy,” Brooks said. “The idea of a compilation made me nervous because it’s looking backwards. But what we had (with ‘Simpsons World’) was a lot of brilliant work happening between two groups who really came together. This app is extraordinary in that for the first time it puts all the work we’ve done on the series and our mobile games under one roof. It is limited only by our imaginations.”

The development of “Simpsons World” started with research and focus group testing to determine what exactly the most ardent fans wanted out of an on-demand “Simpsons” service.

The app, which does include commercial spots in the full episodes and some clips, allows lean-in users to customize their searches for episodes, clips, information, script details and such in all manner of ways. It offers myriad options for setting up thematic lists of episodes. It also caters to lean-back users by serving up a daily episode selection.

“Simpsons World” is home to all 552 episodes from the past 25 seasons. And in a break with SVOD tradition, new episodes from the current 26th season are available via the app the day after premiere on Fox. In Janaury, a second phase of content will be added including an interactive episode guide integrated with original scripts, notes and related materials.

Saftler, president of program strategy for FX Networks, credits the ingenuity of the app to the hands-on approach taken by the show’s creative team.

“They became fascinated by the potential of a non-linear ‘Simpsons’ world and with their intellectual curiosity and excitement, it was a tremendous creative process,” Saftler said.

The app took its name and much inspiration from the “Simpsons World” book, an all-encompassing guide to the show’s first 20 seasons, penned a few years ago by Groening. From that base, the task force of “Simpsons” creatives and FX execs met regularly with the digital design gurus to map out every inch of the universe.

Key FX Networks execs along with Saftler included marketing prez Stephanie Gibbons, consumer marketing senior VP Sally Daws and digital media marketing VP Jason Phipps. FX staffer Josh Van Hout took on the crucial job of cataloging all of the episodes for the purposes of slicing and dicing them into thematic packages.

“It took him three months to watch all 552 episodes and make notes on every episode,” Saftler said.

For Saftler, the “Simpsons World” launch caps a 12-month period that he calls “the best professional experience of my career.” More than any other exec, Saftler went out on a limb to bank on the ability of “Simpsons” to bring much-needed audience to the comedy-themed FXX spinoff cabler that launched in September 2013.

The “Simpsons” syndication deal came to a head right around the time that FXX launched (on the back of the former Fox Soccer Channel) with the goal of being a younger-skewing comedy companion to the drama-heavy FX mothership. FX had shifted key series including “It’s Always Sunny in Philadelphia” and “The League” to the new channel, but Saftler knew that the channel would need much more heft to get real traction with viewers in the 20-something set.

FX Networks’ purchase of “Simpsons” was not a slam dunk, despite the corporate ties within Fox, and bidding was fierce with Turner, USA Network and Viacom cablers also in the mix. There was talk of possibly parceling out the episodes among two cablers, just because the cost was astronomical for so many episodes. FX Networks execs decided early on that it had to be all or nothing. There would be no room to share “The Simpsons” with any outlet other than Fox for the first-run segs.

While the dealmaking was playing out, Saftler got the idea for launching with a marathon — another point that had to be negotiated as part of the overall sale (and another point that also made Brooks nervous at first). After crunching the numbers, the FX team realized the 12-day time span of the marathon would be a great marketing stunt to help put FXX on the map. Even in his most optimistic forecasts, he had no idea that Homer and Co. would make FXX the top-rated cabler in the adults 18-49 for most of those dozen days of “D’oh.”

“The feeling was that we needed to make an impact, and there’s no show that had this many episodes and so a marathon was a really amazing way to event-ize ‘The Simpsons,’ ” Saftler said. The all-encompassing marathon was a one-shot affair. Contractually, FXX doesn’t have the right to do it again, although it has plenty of flexibility to program 24-hour thematic marathons.

The same team that worked on the app created a marketing campaign for the marathon that was worthy of a series launch, Saftler added. Brooks concurred that the enthusiasm behind the marathon planning went a long way toward cementing the relationship between the camps.

“The worst thing that happens to you as a writer is you have a passion and an energy for something and other people look at you like you’re nuts,” Brooks said. “In this case, we were sitting in a room full of people who had our passion and energy. So nobody’s nuts. That is a remarkable atmosphere to work in.”

Saftler’s faith in the marathon was vindicated. Not only did it generate a flood of media coverage, but the outpouring from fans, “Simpsons” creatives past and and present on social media made it a cultural moment that drove viewers to find FXX on their cable boxes.

FXX at its launch last year was ranked No. 97 on the list of top 100 ad-supported cable networks. Since “The Simpsons” marathon, it has been hovering around No. 24. The median age pre-marathon was 36; today it’s around 28. The subscriber base has inched up to 76 million homes this year, from 72 million last year, but there are gains to come, Saftler said.

“The Simpsons” now airs in strategically situated blocks throughout the week on FXX. Sunday’s 4 p.m.-8 p.m. block always features episodes curated to tie in with the theme of the Sunday 8 p.m. original episode bowing on the Fox network.

” ‘The Simpsons’ has a halo effect on our movies and our latenight lineup,” Saftler said. “FXX really needed ‘The Simpsons’ to give it the ratings tonnage and flow of audience for people who watch the other type of programming we have. It was a crucial part of our strategy.”

Seeing the immediate impact that the show had on a fledgling channel underscored for Saftler (who is “Simpson-ized” below) what a valuable asset “The Simpsons” is for 21st Century Fox, and what a unique pedestal it occupies in pop culture.

“We are three years ahead of where we thought we’d be at this time (with FXX) and we’re prepared for the future of television viewing with (‘Simpsons World’). And all we did was find ways to exhibit the extraordinary work that has been done over the past 25 years,” he said.