The co-writers of KPop Demon Hunters — Netflix's most-watched movie of all time — are developing a crime drama at FX called A Really Bad Person, with Legendary Entertainment and FX Productions co-producing. Danya Jimenez and Hannah McMechan will write the project and executive produce alongside Brett Baer, Dave Finkel (who will supervise), and Sharon Hall, according to Deadline.

The premise is tight and unnerving. A relatable American girl, visiting London, pretends to be the missing daughter of a British family — a last-ditch bid for citizenship, a fresh start, and an escape from a complicated past. It is the kind of logline that fits the crime-drama lane FX has built its scripted reputation on, and the first live-action project for a writing team best known until now for animation.

Jimenez and McMechan co-wrote KPop Demon Hunters with directors Maggie Kang and Chris Appelhans. The film racked up 325 million views in its first 91 days on Netflix and has since surpassed 650 million views to date, making it the platform's most-watched movie ever, per Deadline. It also swept the major animation awards: the Academy Award, the Golden Globe, and the Critics Choice Award for Best Animated Feature.

That is not the only project keeping the pair busy. They were also tapped to write a remake of Attack of the 50 Foot Woman, currently in development with Tim Burton, Warner Bros., and LuckyChap. So A Really Bad Person arrives as part of a broader run, not a one-off pivot.

On the production side, Legendary Television has been building a roster of high-profile genre series — Monarch: Legacy of Monsters on Apple TV+, Dune: Prophecy on HBO, and an upcoming untitled Monsterverse series for Apple TV+ starring Wyatt Russell. A character-driven crime drama co-produced with FX Productions would sit as a different kind of bet for the company: smaller in scale than a monster franchise, but carried by a writing team with a genuinely startling track record.

For now, A Really Bad Person is in development, meaning FX has not yet ordered a pilot or a full series. The writers' room, the cast, a shoot date — none of that exists yet. What does exist is a script commitment from a network that has spent years betting on distinctive crime voices, attached to two writers whose last project broke the all-time viewership record on the world's largest streaming platform. That combination is enough to put the title on the radar, even with no airdate in sight.