In “Strange World,” the world may be super-weird, but those who populate it are some of the most realistic and well rounded that Walt Disney Animation Studios has ever presented. Ergo, it’s the characters as much as the environment that make this vibrant, “Journey to the Center of the Earth”-style adventure movie colorful and diverse in all the best ways. Great as the people and places they explore may be, however, the relatively unimaginative story consigns this gorgeous toon to second-tier status — a notch below director Don Hall’s earlier “Big Hero 6” — instead of cracking the pantheon of Disney classics.

“Strange World” centers on a civilization called Avalonia, which is surrounded by “an impassable ring of mountains.” A sudden (and somewhat underexplained) resource shortage drives three generations of the intrepid Clade family to face the unknown. Swarthy, macho granddad Jaeger (voiced by Dennis Quaid) attempts to forge his way directly through the formidable mountains with his more cautious son, Searcher (Jake Gyllenhaal). A quarter-century after that mission goes south, Searcher sets out — this time underground — with his own teenager, Ethan (Jaboukie Young- White), along for the ride.

Down below in Strange World, they discover an astonishing ecosystem, full of bubble-gum-pink trees and floating streams of sashimi-shaped creatures. It’s a dazzling new environment — full of kooky Dr. Seuss-worthy flora and fauna in off-kilter textures and hues — that capitalizes on the fact that we don’t know whether we’re in inner space, outer space or somewhere else altogether. Production designer Mehrdad Isvandi’s constantly surprising “Forbidden Planet”-meets-“Fantastic Voyage” aesthetic keeps us guessing, testing our prejudices about organisms we don’t recognize.

The same goes for the Avalonian characters, who come in a refreshing range of shapes, colors and configurations, from the three-legend pet dog Legend to Ethan’s biracial family. Avalonia itself looks a lot like a Swiss farming community, albeit one that gets a nifty steampunk upgrade soon after Searcher discovers a glowing plant he calls “pando” during the film’s prologue — rendered in a visually appealing, Ben-Day-processed style that gives the film a classic pulp comics flair early on.

Mission accomplished, as far as Searcher is concerned: Pando is a renewable power source — literally, “green energy” — and what could be better than that? Searcher is far better suited for farming than roughing it like his father, which keeps the adventure-averse family man busy for the next 25 years — until such time that the pando crop starts to fail and Avalonia president Callisto Mal (Lucy Liu) enlists them for the outing to Strange World. Gyllenhaal is great at playing the overprotective dad who’s also progressive-minded enough to realize he doesn’t want to be the bossy control freak his own father was. When Searcher orders Ethan to stay home, it’s no surprise that the boy disobeys, stowing away in the pando-powered airship as it takes off to save the precious plant on which Avalonia depends.

Once they reach Strange World, Ethan’s personality proves to be an asset, as these human characters face species the likes of which no one has seen before: Day-Glo pterodactyls, floating pink pancakes and land masses that walk on giant elephant legs. While Dad’s hyper-cautious, Ethan is more trusting of the unfamiliar life-forms they encounter, adopting an amoeba-like blue blob he dubs “Splat.” It’s a testament to the animators that this critter — which stretches like a sticky-hand toy and sounds like a kazoo — still manages to be adorable, even without googly eyes (or anything remotely resembling a face). And guess who they should find down there but Searcher’s own long-lost pop, unlocking all sorts of daddy issues.

Clearly inspired by the spirit of Jules Verne and H.G. Wells, writer (and co-director) Qui Nguyen concentrates on the father-son dynamics between these characters. There are environmental themes too, obviously, which set up a big third-act twist, but the movie’s organic message — instructive without being preachy — comes down to: Teach your children well … and you may wind up learning from them in the end. Heck, Graham Nash’s folk-rock classic would’ve made a fine theme song if the filmmakers hadn’t ordered up a grand John Williams-style orchestral score from composer Henry Jackman (who supplies goofy family anthem “They’re the Clades!” instead).

Looking back through Disney’s toon catalog, you’ll find the studio alternating more or less evenly between films that skew boy- or girl-centric, with “Treasure Planet” on one hand and most princess movies on the other. “Strange World” may focus on helping its dudes work through their issues, but it offers no shortage of strong female role models — like Clade matriarch Meridian (Gabrielle Union) — or people of color. In fact, this may be the first Disney film (not counting “The Jungle Book” or “Zootopia”) to show characters of varied backgrounds coexisting as they do in real life.

It’s starting to feel like Disney woke up and realized that the families, friend groups and greater society around them aren’t homogeneous, and that the studio has been out of touch when confining them to separate cultural bubbles. That’s not a dis against “Mulan,” “Moana” or “Encanto” — each of which made pioneering strides toward broadening Disney’s horizons — so much as an enthusiastic endorsement for presenting a world in which diverse identities commingle more than they clash.

By far the most overdue of these innovations is the way Ethan has a crush on a boy named Diazo (Jonathan Melo) … and everyone is cool with it. The only drama that subplot generates is whether Ethan will find the nerve to tell Diazo how he feels — although it’s pretty clear Diazo already knows, and shares Ethan’s feelings. Sure, some countries will lose their minds over there being a gay character in a Disney movie, which makes it all the more courageous that producer Roy Conli deemed it time to expand the studio’s “Someday My Prince Will Come” idea of romance. It’s normal that some kids should feel as Ethan does, just as it’s normal that his mom is also a pilot. It’s those who think otherwise who are living in a strange world.