I want everything to stay exactly like this and never change.

This is going to be more of a highlight reel than anything comprehensive – partly because it’s twice as long as “Change Your Mind”, and partly because there’s surprisingly little substance overall. Most of it is fanservice, as the creators are obviously enjoying the creative freedom of a bigger budget and a longer runtime. Personally, I’m not terribly fond of it, but I’d say if you’ve watched the rest of the series, you owe it to yourself to watch it at least once (though I’m still not sure if it’s crucial set up for Steven Universe Future or not).
The movie opens with an extremely Disney credits sequence (complete with storybook!), and uses the storybook motif to recap the events of the series. It can seem a bit cloying at times (especially the first time through), but at least it makes sense in context. Said context being that the Diamonds are explaining these things to their people in anticipation of their formal request that Steven assume Pink Diamond’s throne and move to Homeworld, so of course they’re going to sing his praises. But he politely defers.
Steven: As much as I’ve loved dismantling the empire and saving all your planets, I can’t wait to get home and spend some quality time with my friends!

This is one of the fun things about the heightened production values: They can actually animate dresses!
And yes, I can confirm that the Diamonds can still be kind of annoying in this movie even if you do approve of the general direction of their characters.
Steven: You guys have really gotten better at showing affection, but I’ve got my own life to get back to. Don’t forget, I’m not Pink Diamond.
Diamonds: Yes we know that you're not her But you were hers You know what it meant to love her And you remind us so much of her
Because they have a budget and they’re gonna cram in a song anywhere they can!
Yellow Diamond: I’ve disbanded my armies! I’ve liberated my colonies!
Blue Diamond: I never shatter, I never make anyone cry!
White Diamond: I’ve been saying please and thank you, even to lower life forms!
Steven: What did we talk about?
White Diamond: Equal life forms…Steven, we’ve done everything you’ve asked!
Steven: That’s great! Good job, keep it up. Bye!
Yeah, I’m with Steven. Good on them for finally starting to act like decent people, but he’s still got his own life to live.

Connie remains adorable, and Connie and Steven are adorable…but she kisses him (on the cheek) for what seems like the first time, so it seems their relationship hasn’t changed a ton over the last two years, which to be fair, he was out having space adventures for most of that time while Connie’s still in school. I’d make a bigger fuss if it weren’t addressed in Future.
Anyway, the next number is primarily concerned with recapping the character development for the (main) Crystal Gems, which is sadly going to prove necessary for the plot of the film.
Once upon a time I burst to life inside of the Kindergarten A product of a war that I had no idea I had a part in I came out late and alone Knew nothing but my home But I know now exactly who I'm supposed to be And it's a part of this family Here we are in the future Here we are in the future and it's bright Nothing to fear, no one to fight I can't believe we've come so far Happily ever after, here we are!

I’ve gotta say, I do love the little ways Steven uses his powers, like bubbling food to save it for later, or applying his magic spit to the stem when he picks a flower so it grows right back. Because this boy is still precious.
If I could just stop right here and be Finally done, finally us, finally we
Then he goes and jinxes it by wishing that everything could just stay perfect forever.
Which leads us to one of the highlights of the film, Spinel.

Like, I can tell that the animators had a blast with her noodly limbs and cartoon physics, not to mention that she graces us with the show’s only real villain song (I mean, there are a few songs sung by villains, but this one is blatantly a motive rant for Steven’s benefit and also just has fantastic energy).
Who am I? Who am I? What are you even saying? I'm the loser of the game you didn't know you were playing Let's play another game, this time I get to win! Life on the line, winner takes all, ready or not let's begin! Oh, that's right I heard the story over and over again Gee, it's swell to finally be her other friend Oh, that's right I heard the story, don't really like how it ends Gee, it's swell to finally be her other friend
Unfortunately, this doesn’t actually tell Steven much about her. Pearl recognizes her from somewhere (presumably yet another Gem from Pink Diamond’s past), but before they can actually talk, Spinel manages to poof all the others and hits Steven with the same ominous pink weapon before he gets a hold of it and poofs her.
Thus we get to the main plot, as the weapon essentially wipes Gems and returns them to factory settings – or as Peridot succinctly puts it, wipes out their character development! So Steven’s left with a Pearl who happened to latch onto Greg as her new master, Sapphire and Ruby being…well, a normal sapphire and ruby, Amethyst mostly just mimicking and/or repeating people, and Steven being set back nearly to his power level at the beginning of the show (only nearly because at least he knows how his powers are supposed to work and thus can kind of almost manifest them).

Then there’s her. Now that her memory’s been wiped, she’s decided to become Steven’s best friend and follow him everywhere. She isn’t quite as annoying as she could’ve been, partly because her desire to be friends at least seems genuine, and partly because the other blank-slate Gems are also annoying and unhelpful. You see the problem.
But at least there’s one upside to this whole mess: The B-squad finally gets a chance to shine!
Steven: Here she is. My new best friend Spinel. […]
Bismuth: I thought you said she was just trying to kill you!
Lapis: Wow. Quick turnaround.
Peridot: No kidding. It took me months to stop trying to kill Steven.
Bismuth: Took me about a day, day and a half.
Lapis: I’m still on the fence.
And they even get to sing, proving that Bismuth (Uzo Aduba) actually has a pretty great alto.
When has it ever been easy? Hasn't it always been hard to be us? When you go against the grain, there's always somebody around you can't trust That's why we've got to have each other, while we figure this out we must Because we are the Crystal Gems And we never give up, we never give up on our friends! As long as one of us is standing to brandish the star We'll find a way to save the day, that's who we are!

Anyhow, Spinel suggests that in order to get all the Crystal Gems back to normal, they just need to simulate all the different “pieces” of their lives, and somehow this will actually work.

But at least it garners a sort of transformation sequence for Garnet (which is admittedly pretty sweet). That’s kind of my feeling about the majority of the movie: It’s pointless, but at least it all looks/sounds great!
So Garnet is together again, but apparently she’s still missing “a piece” and doesn’t have her memories back, so Steven decides to go look for Amethyst, leading to our first hint about Spinel’s damage.
Steven: Spinel, you stay here with the others, and I’ll be right back…
Spinel: No!
Steven: Okay…let’s go together?
This is the first time since reforming that Spinel’s “broken character” and expressed a negative emotion…

Then, once Steven finds Amethyst, he sets about giving her all the “pieces” by singing and dancing about how he’ll always be there for her and it is just so precious. Also apparently he has tap sandals.
In the dark of the night In the light of the day When you're rising to shine When you're hitting the hay Just remember this song How's it go, I forgot I'm gonna be right by your side no matter what Through whoever you've been Through whoever you'll be Through whatever you lose You will always have me At the end of your rope I'll be holding you tight I'm gonna be right by your side no matter what
By the end of the song, Amethyst has regained all her memories, so that’s one bullet dodged, just two more Crystal Gems to go…but then Steven realizes he needs Spinel to regain her memories, too, because she kind of set off a doomsday device and can’t remember what it even is, let alone how to turn it off. So the next step is to reboot Pearl, since she was the only one who had any idea who Spinel was before. And while I find the blank slate Pearl the most annoying, I am grateful for Pearl’s plotline for precisely one reason: Steg.
Steven: Come on, Dad. Let’s duet.

THIS SHOW. I can’t even.
Nothing is holding me back now No one can push me around What do I wanna be? I'm the master of me And isn't the thought enough to lift me off of the ground? We could be independent together! Independent together we could fly

Just look at this candy colored fever dream. There are no words.
But Spinel is (understandably) feeling left out, and Steven ends up chasing her all the way back to her old home with Pink Diamond.
Spinel: This was our garden – a special world, built just for Pink and I. On Homeworld, Pink was so lonely and sad, but not here! Here, we would play for hours. Every day was so much fun. At least, that’s what I thought.
Steven: Did something happen?
Spinel: Pink wanted a colony more than anything. One day, her wish came true! Blue and Yellow gave Pink her very own planet – Earth! I was so excited. A brand new place to play!

Here in the garden Let's play a game I'll show you how it's done Here in the garden Stand very still This'll be so much fun And then she smiled That's what I'm after The smile in her eyes, the sound of her laughter Happy to listen Happy to play Happily watching her drift away Happily waiting All on my own Under the endless sky Counting the seconds Standing alone As thousands of years go by Happily wondering Night after night Is this how it works? Am I doing it right? Happy to listen Happy to stay Happily watching her drift away You keep on turning pages For people who don't care, people who don't care about you And still it takes you ages To see that no one's there See that no one's there Everyone's gone on without you Finally something Finally news About how the story ends She doesn't exist now, survived by her son, and all of her brand new friends Isn't that lovely? Isn't that cool? And isn't it cruel? And aren't I a fool? To have happily listened Happy to stay. Happily watching her drift away

I think a lot of people saw this and thought it made Pink Diamond an “irredeemable” villain, but if that’s what you see, then I think you’re missing the point – not necessarily the point of the movie, or even this sequence, but a point that the whole series has been building towards, which it leans into hard in Steven Universe Future: No one is irredeemable, and no one is perfect, either. We’re all just people, with plenty of good and bad, and a lot of that comes from the way we’re raised. Pink Diamond was raised to literally objectify people, so it made sense that once she “outgrew” Spinel, she would toss her aside. The way I see it, she probably did feel guilty about it at first, but with all the new responsibilities of being a dictator (combined with the pressure from the other Diamonds to “grow up”), she managed to push those thoughts aside, wanting to forget. I’m not saying it was right, just understandable.
Steven: You deserve a better friend. Spinel, come back and save the Earth with me. You can start over there, make new friends.
Someday, somewhere, somehow You'll love again You just need to find someone Someone who treats you better Someone who wants you around Someday, somewhere, somehow You're gonna feel found
So he convinces Spinel to shut off the doomsday device…at least until she realizes that he doesn’t really have anything figured out beyond that. One misunderstanding later, she’s reactivated it and generally gone full villain again, just slightly more bitter.
Spinel: You know, I came here to take my anger out on a bunch of strangers, but now that I know you, I want to kill you even more.
Steven: I don’t get it! Why aren’t my powers back? Aren’t I reliving every horrible thing that’s ever happened to me? A Gem I barely know is trying to kill me, I’m paying for stuff my mom did that had nothing to do with me. I’m struggling with my powers, the world’s about to end – what piece could I be missing? This is the story of my life! […] I changed. That’s the final piece. All those struggles, I learned from them, and I grew! All this happily ever after stuff has made me forget the first power I ever had – the power to change!

There you go – the only piece of actual character development for any of the main characters in this movie. I honestly feel like they could’ve fit this story into a regular ten minute episode without much trouble (or at least a twenty minute episode). But this is what we got.
Spinel: You can’t change the way I feel!
Steven: That’s right! Only you can.
You can make it different You can make it right You can make it better We don't have to fight You can make an effort Starting with tonight Cause you can make a change
Spinel: Just can it, won’t ya? You can’t just make everything better by singing some stupid song! All that stuff’s easy for you to say. When you change, you change for the better. When I change, I change for the worst! I used to be just not good enough for Pink, but now, now I’m not good at all! So funny, right? At least you found me entertaining. You actually liked me, didn’t you? What am I doing? Why do I want to hurt you so bad? I’m supposed to be your friend. I just want to be your friend.
This is one theme that does end up carrying over to Future, the idea that pain doesn’t automatically equal growth for everyone.
So they manage to destroy the device in the fight, and somehow that means the world isn’t ending anymore? Despite all the toxic pink goop? I guess I should just be glad that it’s over.
Spinel: But what about the poison, what about the planet, what about your happily ever after?
Steven: There’s no such thing as happily ever after. I’ll always have more work to do.

I mean, technically they address the poison thing, but I still find it hard to believe that even Steven would be able to kiss the whole planet clean, let alone that he could do it in anything like a timely fashion (there’s a time-lapse montage, but it’s still kind of implied that there wasn’t more than year between the end of this and the beginning of Future, so…).
And for an even easier resolution, the Diamonds just happen to drop by looking for some replacement for Pink Diamond that they can shower their affection on, and Spinel is looking for someone she can befriend that she hasn’t brutally attacked recently!

I'll be ready every day For as long as I can say Here I am in the future with my friends That's why happily ever after never ends
Then they just top it off with a Vegas number, because why not? Seriously, “Why not?” is the entire underlying reason for this movie’s existence. I feel like I would’ve preferred if they’d had significantly less stuff going on, because it might’ve been nice to just see them all having fun together for a bit. But considering that they’re used to filling out all the time they’re given with content, I can’t say I’m surprised.
Anyhow, I’ll be happy to return to the regular episodic format next time…
…in the Future!