It turned out to be a good thing that reptiles were left out of Disney’s Oscar-winning Zootopia. There just wasn’t room for them in the sprawling, mammal-oriented metropolis. But this enabled directors Jared Bush and Byron Howard to introduce reptiles in Zootopia 2 and build a Chinatown-like murder mystery around why they were banned 100 years ago.

Leave it to newbie cop partners Hopps (Ginnifer Goodwin) and Wilde (Jason Bateman) to interrupt the Zootennial celebration with the revelation that the scene-stealing blue pit viper Gary De’ Snake (Ke Huy Quan) has stolen an ancient book from the powerful, Succession-inspired Lynx family. This concerns the original design of Zootopia’s weather walls between biomes.

The bunny and fox are definitely past their honeymoon phase in the sequel. Their differences become much more magnified, with Hopps compelled to always prove herself and Wilde always leaning into his street smarts and quick wit. Thus, intimacy becomes a problem. In fact, their relationship is a microcosm of a larger theme about learning to communicate to overcome differences between species.

“As we were diving into the story, there was a lot of debate about the amount of time that should have passed between the first movie and the second,” said Howard, who directed Zootopia with Rich Moore. “We started with a five-year gap. But we really felt like you missed out on a lot of the really critical relationship milestones. We needed to start this movie right after they team up and it’s all brand new.”

Meanwhile, the more expansive world building needed to reflect a darker and more dangerous murder mystery about the origin of Zootopia. “I think, coming into this one, we wanted to expand what people knew of this city of Zootopia,” said Bush, Disney Animation’s chief creative offer, who co-scripted Zootopia. “Because there were all these environments and neighborhoods that we didn’t get to explore in the first film. I think Byron and I always felt there was so much more to find.

“And, for this film,” Bush continued, “thinking about what type of places we wanted to make Nick and Judy go to, they really put them out of their comfort zones. Nick was such an ambassador to Judy in the first film. He knew everything about Zootopia. So we really wanted them to have to go to places that he wasn’t familiar with. That took away his ability to be the most knowledgeable character in that dynamic.”

The ingenious weather walls become the McGuffin. “You have this giant weather apparatus that separates the heat and the cold,” Bush added. “That really goes to the research that we did early on in the first film.”

Everything about Zootopia 2, though, is bigger and more thrilling, including the addition of several action set pieces. The best is set in Marsh Market, a vast pier location on the swampy outskirts that serves as a port for shopping, eating, and entertainment. That’s where Hopps and Wilde are escorted by beaver conspiracy theorist/podcaster Nibbles Maplestick(Fortune Feimster), and where they discover a secret reptile hideout.

“Marsh Market was designed for animals that live both above and below water,” Bush said, “and there’s no real world human equivalent to that. We knew from the beginning, not only did we want to go there and spend time with these walruses, sea lions, and otters, but we wanted there to be a chase out of that location with water.”

Howard added that they previously introduced the water tube station with hippos at the beginning of the first movie and wanted to take a deeper dive into the infrastructure of this city. “We’ve already established that Nick and Judy are somewhat uncomfortable here,” he explained. “So it was this really amazing choreography between our production designer Corey Liftis, our layout artist, and our environment artist to figure out how you design a path of this chase that would take advantage of this location. This makes Nick and Judy improvise in this world.”

Another chase occurs at the midpoint, high in the mountains at the Honeymoon Lodge. “We knew that moment needed to be about separation and to physically be able to visualize that with that lodge coming apart at the seams,” Bush recalled. “We told our team that we wanted to it, and they were like, ‘OK, we’ve got to shake hands and agree that this is exactly how this set comes apart.’ Because a lot of people were going to work on this at the same time. And what I love is that it’s a completely different flavor than the other parts of the film.”

The visual effects team, led by Gregory Smith and the legendary Marlon West, upped its game throughout. “This is one of the biggest films we’ve ever done at Disney Animation,” remarked producer Yvett Merino. “And I think that’s true on all levels from world creation and characters all the way through effects and lighting. Because we used Presto [software] on this film, the animators and the effects team were able to collaborate a lot more while they were working on the shot at the same time. And the effects team would be able to put their effects in that impacted animation or animation would move around and have effects react to that.”

The final action sequence at the weather station in tundratown contains its own mayhem, once again putting Hopps and Wilde in unfamiliar territory. “We knew that we wanted to end the movie in that place, and that puts Nick and Judy at a disadvantage,” Bush said. “But you want to be looking at that through an entertainment lens more than anything else. But it does feel like it may turn into something quite traumatic. Ultimately, what you want is just to see Nick and Judy as their best selves.”