After the craziness of the past few episodes, this one takes things down a few notches, focusing on the sisterly duos of Rarity & Sweetie Belle and Applejack & Apple Bloom.
Rarity awakens one morning to the smell of a delicious breakfast and...smoke? It can only mean one thing: Sweetie Belle's cooking. Sure enough, Rarity finds her sister in the kitchen, annoyed that her surprise breakfast-in-bed plan has been found out. Rarity also finds her parents, pleased as punch at the charred work of their youngest daughter. They're dropping off Sweetie Belle, since Rarity promised to watch her while they're on vacation, which Rarity had completely forgotten about.
As soon as their parents pull away, Rarity heads back into the kitchen to cook them both a proper breakfast. Though she promises Sweetie Belle can help, she ends up doing most of the work herself, until Sweetie Belle complains. So Rarity lets her place the garnish on the plates. However, she micromanages the whole process, which causes Sweetie Belle to slip and knock everything off the table. The garnish does land perfectly, though.
By the time the kitchen is cleaned up, it's time for Rarity to get to work, so she has Sweetie Belle take the used towels to the laundry room. Her little sister, wanting to be useful, takes it upon herself to do the laundry, which wouldn't have been a problem, except that she included Rarity's incredibly expensive, one-of-a-kind designer crocheted wool sweater. Which promptly shrinks. With great effort, Rarity manages to control her anger, and heads back inside, warning her sister to stay out of trouble.
But Rarity's boutique is not that kid-friendly, and Sweetie Belle soon finds herself bored out of her skull. Remembering her sister's warning, she spots some crayons and paper, and since she's never been yelled at for drawing, gets to work. She feels her artwork needs a little something extra, and she proves she is most definitely Rarity's sister when she decides that something is pretty light blue gems, and Rarity just happens to have a whole trunkful. But when she shows Rarity the finished product, it creates screams of horror rather than delight. It seems that these were no ordinary gems, but extremely rare baby blue sapphires, which Rarity procured for a very important client's outfit. And Sweetie Belle used every single one. Going off to get more, if she even can, Rarity instructs Sweetie Belle to clean up the art supplies, and to try and find something to do that doesn't end in a big mess.
But not for long, once she sees what Sweetie Belle did to her workshop. The entire room is tidied up and organized, much to Rarity's dismay. Sweetie Belle is confused by Rarity's reaction, since normally the unicorn is all about cleaning and being organized. But her workshop is the one place Rarity needs a mess for inspiration, and now she has to start all over. With even greater effort, Rarity keeps her temper in check, telling Sweetie Belle she just needs some alone time.
So Sweetie Belle, feeling low, heads into town, where she runs into Apple Bloom, who is promoting the heck out of the Sisterhooves Social. She plugs it as the sisterly bonding activity Sweetie Belle and Rarity need, and Sweetie Belle immediately agrees. However, when she brings it up to Rarity, her sister disagrees, mostly because it's being held at Sweet Apple Acres. Sweetie Belle insists that any sisters who care about each other go to the social, but Rarity counter-insists that playing around in the dirt is just too uncouth for her to deal with, sisterly or not. This is the last straw for young Sweetie Belle, who renounces Rarity as her sister. Rarity is shocked and annoyed at this, feeling that if anyone should be renouncing sisterhood around here, it should be her, based on all the trauma Sweetie Belle has put her through. Tempers flare, and Sweetie Belle storms out, which suits Rarity perfectly fine.
Sweetie Belle airs her woes at Sweet Apple Acres, where Applejack, Apple Bloom, and Big Macintosh are getting things ready for the Sisterhooves Social. Applejack advises her to just give Rarity a little time to cool down, and asks her to help them get ready. Sweetie Belle is hesitant, considering her earlier forays into "helping," and is mystified when she sees how Applejack and Apple Bloom have turned collecting bruised apples into a game. Her try doesn't go as well, and seeing how well Applejack and Apple Bloom work together just reminds her of how Rarity wouldn't let her help out. Speaking of Rarity, she's still fuming over Sweetie Belle neatening up her workshop, until she notices how her fabrics are now lined up in rainbow order. This inspires her for a new line, which she dubs Full Spectrum Fashions. Despite this, she's still miffed over Sweetie Belle's unsolicited help.
Back at Sweet Apple Acres, Apple Bloom gets a turn at stomping on grapes for grape juice, but gets a little overenthusiastic and splashes Applejack. To Sweetie Belle's surprise, Applejack doesn't get mad, but just joins her in the tub to get her covered in grape juice, too. Meanwhile, Rarity prepares to wash her latest creations, but spots her shrunken sweater and fumes again. Until she realizes it's the perfect size for Opal now. Still, she isn't quite ready to forgive her little sister. Applejack and Apple Bloom corral some sheep, amazing Sweetie Belle with their oneness of purpose. And Rarity finishes up her commissioned outfit, but needs just one more sapphire. Again raging at the Sweetie Belle-emptied trunk, she goes to see if she can't pry one off of her sister's art project. And is rendered speechless, as this time she actually sees the image: her and Sweetie Belle, surrounded by a heart of sapphires. Seeing this, she dramatically agonizes over the way she treated her one and only sister, and with a speech inspired by Gone With The Wind, she vows to get Sweetie Belle back and make it up to her!
Sweetie Belle is still miffed, but when Rarity apologizes, she tells her that spending the day with Applejack and Apple Bloom has shown her she needs a sister. Just not Rarity. So instead, she's decided to make Applejack her new sister, which is a shock to everyone. Applejack tries to get her to reconsider, and Apple Bloom refuses to share her sister. So Sweetie Belle suggests that Rarity take on Applejack as her new big sister, to show her what a sister should be. Rarity insists she doesn't need lessons on sistering, and to prove it, offers to teach Sweetie Belle all manner of things that she (but not necessarily Sweetie Belle) enjoys. Sweetie Belle is having none of it, and huffs off. Rarity complains to Applejack for making her look bad, but Applejack just explains to her that being sisters is like apple pie: it's only together that they become something special. Once this sinks in, Rarity realizes what she has to do!
On the day of the Sisterhooves Social, Sweetie Belle checks out the various competitions with Applejack and Apple Bloom, and considers what her sister would think of it. As the starting time for the big obstacle course race arrives, Applejack gives her their surprise: she gets to be Applejack's honorary sister for a day and run the race with her. Sweetie Belle is overjoyed, but Apple Bloom is quick to emphasize the "for a day" part. Repeatedly. Granny Smith announces the beginning of the race, and the five sister teams get started. Sweetie Belle skips across the mud, but Applejack falls in, covering herself head to toe. But she continues on, and the two of them move on to the next obstacles, passing each one with ease. Though they seem to have the lead, another team comes up from behind, giving them a challenge. In the end, it was close, but the other team made it across the finish line first.
Sweetie Belle doesn't care, though, as she just had such a good time. She leaps up to give Applejack a hug, knocking off her hat and revealing a horn? Sweetie Belle pushes more of the mud off, revealing it was Rarity all along! Applejack explains that they switched places at the mudhole so that the two sisters could compete together. Even Apple Bloom was in on it. With their sisterly bond repaired, Rarity suggests celebrating at the spa, but no one takes her suggestion seriously.
After a week's worth of sisterly activities, Rarity and Sweetie Belle have Spike take a letter for the princess detailing what they've learned about being sisters: it isn't easy, it takes teamwork, compromise, and accepting each others differences, but mostly it's about having fun together. The two fail to agree on how much dirt that should entail, so Spike intervenes, and all ends happily.
I'll admit, the first time through, I totally did not pick up on the whole Rarity and Applejack switching until the reveal, but if you go back and watch, sure enough, "Applejack" has Rarity's blue eyes.
Applejack and Apple Bloom
Sweetie Belle is touched