For six years now, Cartoon Network’s “Steven Universe” has been pumping out story after graceful story about the power of love, friendship, cooperation, self-acceptance and trust. Creator Rebecca Sugar, who previously worked on the network’s equally surreal “Adventure Time,” has created and honed an animated galaxy unlike any other, overflowing with distinct characters and complex mythology that sets it apart. So while the show might have started as the simple adventures of a boy and his alien guardians (aka “The Crystal Gems”) navigating what it means to live on Earth, “Steven Universe” has since served up some of TV’s most thoughtful meditations on what it means to be a good and compassionate person — or alien, or half-human/half-alien, or whatever it is that makes your individual atoms so special.

Now, the series is releasing its most ambitious chapter (and biggest reward for diehard fans) yet in the form of a feature-length movie musical, featuring collaborations with artists like Chance the Rapper, Ted Leo, Aimee Mann and more. Picking up two years after the near-cataclysmic events of the show’s latest episode (“Change Your Mind,” which aired in January), “Steven Universe: The Movie” introduces a Steven (Zach Callison) who has matured from a determined boy to a self-assured teenager, with an actual defined neck and everything. (As per Sugar, getting to finally animate Steven’s neck was one of the biggest bonuses of flashing forward.) After learning that his mother isn’t Rose Quartz, as she once claimed, but legendary outlaw Pink Diamond, Steven has made amends on her behalf with the other grieving, combative diamonds (voiced by Lisa Hannigan, Christine Ebersole and none other than Patti LuPone) and ushered in an unprecedented era of inter-dimensional peace. It’s not long before that detente is threatened by a mysterious new gem, but in true “Steven Universe” style, there is a good (and devastating) reason for its malevolent insurgence, followed by a genuinely touching resolution, courtesy of Steven’s enormous capacity for empathy.

Meanwhile, in the time since Steven’s been away, his beloved hometown of Beach City has gotten a makeover that incorporates elements of the alien world from whence his guardians, Pearl (Deedee Magno), Amethyst (Michaela Dietz) and Garnet (Estelle), came. Since much of the action takes place on Earth, the movie’s plot presents less of an opportunity for Sugar and her talented storyboard artists to elaborate on the gorgeous dreamscapes of space that “Steven Universe” has previously explored. Still, the sporadic glimpses of planets past and the dizzying fight scenes display the series’ singular eye for detail and motion. And for longtime fans, Beach City transforming into such a hybrid space (not to mention Steven and friends aging up and into snazzy new outfits) represents a stunning aesthetic payoff to match the evolution of the show and its themes. When “Steven Universe” continues past the point of this movie, it will neither look nor feel quite the same as it once did — and that, as Steven himself eventually realizes, is exactly the point.

Without getting into the particulars of the conflict itself, “Steven Universe: The Movie” is as much an ode to the value of growing and changing as it is a celebration of the series. Pearl’s hard-won independence, Amethyst’s willingness to play nice with others, Garnet’s fierce belief in love, and Steven’s maturity all get moving spotlights, and catchy-as-hell musical numbers besides. It can feel repetitive; the show has already thoroughly explored all of these areas, and the format of “a surprise attack from an unknown gem rival with an unknown connection to our heroes” is one that “Steven Universe” has leaned on again and again. Yet it’s hard to be too annoyed by this fact, especially when Steven explicitly acknowledges it at the movie’s most climactic moment. Though he wanted to believe he and his family had found a “happily ever after” after everything they’d been through, the truth is that, as he says, there will “always be more work to do.” Though the movie could act as a series finale, in this moment, it also makes clear what “Steven Universe” will look like going forward.

There will always be more fights to win, more change to grapple with, and yes, even more friends to make. There will always be moments when they are less assured of themselves and each other, and some need for reminders of who they are and what they value most. Even when they’re sure they’ve figured things out, there will always be room for growing up. “Steven Universe” has infused its world with these themes from the beginning, but with “The Movie,” the series gets to take a victory lap and underline them in neon. Now that the series has reset so many of its biggest conflicts, it may have to find new ways of exploring them — but given its many years of meticulous and wildly imaginative storytelling, future ingenuity feels like a safe bet.

TV movie, 90 minutes. Premieres Monday, September 2 on Cartoon Network.