Luna on Anon on Celestia

"Wait, wait wait, so the used to be big evil pony is our sister?!" you exclaim, looking over at Celestia.
>"We have a big brother?!" the little blue alicorn exclaims right after you, almost bouncing on her hooves.
>Luna, as Celestia called her, jumps up into your arms and nuzzles into your neck in a horsey hug.
>Hugging back uncertainly, you recall what brought you to your current situation.
>In the end, It probably started with when you arrived here in Equestria years ago, and since you didn't have any family here, Celestia, the ruling princess, decided to be your big sister.
>And you're not kidding about "big" sister, she is much bigger than even shire horses, and compared to all the big dog sized ponies around her, she towered over everything, including you.
>You were pretty fine with it, since you were only twelve, and there was no way you'd be able to live on your own here.
>Being a prince was great, though some of the fancy parties were very boring.
>But you're wandering, as just yesterday, your big sis decided to send you to Ponyville, a small town with nothing of real note there save it's hosting the Summer Sun Celebration.
>She also sent one of her students, who was rather insistent on talking with "The first prince of Equestria ever!" despite how boring she was.
>At least her little dragon helper was pretty cool.
>Anyways, you were stuck following the pony around town till you found the mayor, who directed you to a place to wait for your sister.
>Well, she never arrived, and the ceremony started with you and a couple guards waiting in her spot nervously.
>All of a sudden, a giant black alicorn arrived, and began evil monologuing.
>A lot of it was silly nonsense, but the fact she has "gotten rid" of your sister worried you.
>The purple pony your sister sent seems to know who this other pony is, and after some back and forth, the black one disappears, and the purple one runs off.
>After rushing off after her, you find her being confronted by some other ponies, before she notices you as well.
>In rapid fire fashion, she explains everything that went down, and how she needs to find some ancient rocks or something to save your sister or else eternal night or some such nonsense.
>Together, the lot of you ended up going into some forest, where the ponies fumbled around in typical pony fashion.
>How could anyone be scared of trees, honestly.
>Eventually, your little group found an old castle, and some magic rocks and a speech about friendship later, and a giant rainbow was shot at the black horse, and bam, you now have a little sister.
>And you know that's not how it works normally.
>"So you see, Anon, She's only a few years younger than me, though I guess with her current size, she's your little sister for now."
"She's going to grow then?"
>"Noooo, We wish to stay little. We always wished for a big brother to carry us around and protect us," Luna exclaims, squirming in your grip.
>"Some things you can't stop, Luna, but for a while, you will get to have a big brother."
>"Will he carry us?"
"I guess I can. We do need to get back to town for the celebration, big Sis."
>Lowering Luna to the ground, you kneel so she can climb onto your back.
>"What are you doing big brother?"
"You wanted a ride, right?"
>"What are we to do then? Are thou not going to carry us in your arms?"
"Just climb on and rest your front hooves over my shoulders."
>She does so, climbing up your back, and despite her size, she's rather light.
>As you rise up, her grip tightens till you're fully upright, and she starts giggling.
>"We're so tall now, we can look down on all of you but big sister!"
>"Indeed you can, Luna, now let's hurry."
>Keeping up with Celestia when she's running isn't easy, especially with an excited blue alicorn on your back, but you do well enough.
>Years of being a running partner for her has done wonders improving your speed and stamina, since she always needs to run off her cake splurges.
>Still, you're out of breath by the time you reach town, and the two of you slow down to what she refers to as the "regal walk".
>Walking slowly and calmly to allow you to regain your breath while not looking like you're rushed.
>Ponies soon notice their princess and prince returning, and they swarm around you, expressing their concern.
>Questions are asked about the new Alicorn on your shoulders, and she's simply explained as yours and Celestia's sister.
>The ponies do accept this, but after some of the things you have seen here today, you don't question it much either.
>This land works on some completely different rules compared to back home.
>The day goes smoothly after that, and together, the three of you enjoy the celebration.

>With that, you now have two siblings, one who takes care of you, and one who you have to take care of.
>And despite a thousand years or something like that's time, Celestia still remembers the exact date of Luna's birthday.
>Worse than that though, she, in all her wisdom, sees fit not to inform you of it.
>So today, when you came down for breakfast you were greeted by confetti and cake everywhere.
>"It's our birthday!" your little sister exclaims, bouncing up to you excitedly, "What'd ya get us?"
"Celestia never told me it was your birthday, so I couldn't get you anything. Instead, how about I'll do whatever you want today?"
>She stops, her hoof on her chin thinking for a moment, before smiling and saying, "Okay, but you better not forget next year."
>"Instead, for all of today, we want you to ride on Big sis, and carry us on your back so we can be the tallest pony all day!"
"Well, if she doesn't mind, I suppose we can try it."
>Lowering yourself so Luna can clamber onto your back, the little blue alicorn yells out, "Onwards to our sister!" as she climbs up.
>Finding Celestia takes less than a second, as it's hard to miss a near 8 foot tall white horse in a crowd of tiny horses, and getting to her is equally as easy, since the crowd parts for you.
>"Big sis, Big sis, Anon's gonna ride you all day with us on top!"
>Loud gasps ring out through the room, and in the silence that ensues, all can hear your facepalm.
"What she means is for me to sit on Celestia's back while she is on mine so she can be the tallest pony around for her birthday," you say, clarifying Luna's rather misinterpretable exclamation.
>Acknowledgement comes from many of the ponies around, and a few even chuckle at the childish wish, despite Luna being slightly larger than an average full grown pony.
>"Pretty please, big sis?"
>You can't see it, but you're pretty damn sure she's making her cute puppy dog eyes, since you can see the resistance fading in Celestia's eyes.
>With a sigh, she nods, and Luna squeals.
>"Alright, but just for today, since it is your birthday."
>With some magical assistance, you climb up onto Celestia's strong, broad back and sit down.
>"Yay! We're the tallest pony now!" Luna exclaims from atop the stack of royalty, "Now for part two!"
"Part two?" you and Celestia echo, a nervous shiver running down you and into her.
>Suddenly, your vision is obstructed by something brown sliding down over it till a small viewing slit stops in front of your eyes.
>Looking out lets you see Celestia covered in cardboard boxes in the shape of armor, and you must be covered in the same.
>"Super Mighty Mega Princess Knight GO!" Luna exclaims, digging her hooves into your side trying to get you to move Celestia, most likely.
>"Luna, you're being foalish again..." Celestia says, tapping her hoof.
>"It' our birthday, can't we have fun and ride around like our favourite comic hero?
"No, but there are ponies who do this professionally. Why does it have to be us?"
>"Because we want to do it with big Brother and big Sister."
>Celestia gives a sigh that you mimic shortly after, and the two of you nod.
>"Fine, we can do this, but just for today."
"Yeah, just for today is fine."
>Luna squeals with joy, digging her hooves into your side.
>"Onwards for justice!" she shouts out, nudging you and Celestia to move towards the door.
>Before either of you can raise a word of protest, the throne room's main door bursts open, and a deep pink fog rolls in.
>"Oh no, my arch enemy, Dark Lord Ponkus!" Luna exclaims, and a cackle comes from the door.
>"That's right, Mighty Mega Princess Knight Luna, but it's too late, I have with me, My secret weapon!" Pinkie exclaims, walking into view while sporting an eye patch and a curled black moustache.
>"No amount of Evil can stand up to my Hammer of Justice!" Luna yells back, brandishing a broom with a bunch of pillows tied to one end.
>"Oh really?" Dark Lord Ponkus replies with a smirk, "your little hammer is no match for my MEGA DISHARMONY TANK!"
>From behind the fog, a strange box wagon thing with all the ponies who were there when you got Luna in it, each one attached to some weapon or shield.
>"Mega Boom cannon Go!" Pinkie yells, and the cannon attached to Twilight goes off, small pillows raining down around the room, many nobles taking a hit and going down dramatically.
>With her hammer of justice, Luna swats some of the pillows away, laughing at the feeble attack.
>"CHARGE!!" Luna shouts, motioning you to get Celestia to start moving.
>While she doesn't move fast, Celestia does trot forward quickly, nearing the battle tank in seconds.
>"Raise the Squeakershield!" the Dark Lord announces, and with a squeak, Fluttershy is pushed to the front of the tank where she curls up, covered in inflatable toys that form a large bouncy barrier.
>Luna halts you and Celestia, knowing her hammer cannot penetrate that shield.
>"Your shield may be strong, Ponkus, but I have the Mega Dismantler on my side!"
>After an awkward moment of silence where nothing happens, she squeezes your sides, whispering, "That's your cue Big Brother, use your hands to tear down her shields!"
>Raising your arms proves to be a little challenging, but your hands slide out as they do, giving you full ability to grab and remove the inflatables from Fluttershy.
>"Nooo! Retract the shield, fire the Mega Boom Cannon again!" Dark Lord Ponkus exclaims, and Twilight's cannon is aimed down at you.
>Bracing yourself as best you can, the three of you are bombarded with moderate velocity pillows, shaking your stack.
>"Your weapon is no match for our might!" Luna retorts, waving her Hammer of Justice.
>Bringing her hammer down upon the wagon, a cloth sheet rises up to intercept it.
>The hammer knocks the cloth down with it, but under, the wagon is gone.
>"Ha, I see my fabric shroud has you confused," Ponkus taunts, pulling her party cannon out of somewhere, "And now, I will finish you off myself!"
>Still staggered from the pillow barrage, neither you nor Celestia can move to get out of the way, and a blast of confetti and party decorations blind you temporarily and send you to the ground.
>Trapped within the cardboard armor and now pinned by streamers, you can hear Pinkies evil laughter in the background.
>"Haha, Victory is mine!" she exclaims, striking a victory pose.
>"Not so fast!" Luna's voice calls out from above.
>With a gasp, everyone looks up to see her drifting down slowly on her wings, her armor having detached from yours.
>"Evil will never prevail over Justice!" she exclaims, making a dramatic landing, hefting her pillow hammer.
>"Then it's just you and I then."
>"Indeed, and today we face each other for the last time, and we will be victorious."
>What ensues could only be described as a fight that only Pinkie Pie could accomplish with an Alicorn.
>Which is exactly what's happening.
>Luna, with Hammer of Justice in hoof, exchanging strikes with Ponkus, wielding pillow nunchucks.
>The two literally bounce around the room, feathers exploding where their weapons collide.
>If it wasn't so silly, it'd be pretty cool.
>Slowly, Luna takes the lead, landing glancing blows on Pinkie, while it's all she can do to block.
>Backed into a corner, Pinkie looks up as Luna raises her hammer to deliver the finishing blow.
>"Surrender, Ponkus, you cannot win!"
>Hanging her head in defeat, her forelimbs are raised above her head.
>This action causes Luna to lower her guard for just a moment, but it is enough for Ponkus to take full advantage.
>Her hoof shoots to her mane, reaching inside before throwing a small green projectile straight at Luna.
>"Hidden gator strike!" she yells out, a small green alligator biting down on Luna's muzzle, staggering her.
>Swinging her pillowchucks around, she lands a serious hit on Luna's side, sending her tumbling.
>"Any last words, Princess?" Ponkus asks, weapon ready to deliver the finishing blow.
>"Yes, Justice never fights alone!"
>As she says this, nothing happens.
>The silence was so palpable, you could swear a tumbleweed would roll through.
>No, wait, there it goes.
>"Ugh, Brother, Sister, you are soooo horrible at this. You were supposed to run to our aide here. Do you even read the comics?"
>"Yeah, really, I've been practicing my defeat cry for over a week, and I can't do that if I win," Pinkie adds, crossing her hooves.
>With a sigh, you turn to Celestia and shrug.
"Since it's come this far, might as well go all the way."
>"I suppose we should."
>Rising from where you sat, you run at Dark Lord Ponkus, grabbing her in a big hug from behind.
>Celestia knocks her weapons away and subdues the green menace that is the toothless alligator, while Luna rises and readies her hammer.
>"Your defeat is now, Ponkus, and the land shall be free from your tyranny."
>Swinging her hammer in a mighty arc, it collides with Pinkie as you release her, an explosion of feathers and confetti going everywhere, an anguished cry echoing out.
>From inside the storm of feathers and paper, Pinkie disappears, unseen by anyone until the confetti settles.
>There's a brief moment of silence, before cheering and hoof stomping fills the room, the "audience" celebrating the performance.
>Pinkie returns from behind a box with a big smile on her face, bowing to everyone.
>Luna bounces up and down ecstatic before yelling, "BEST. BIRTHDAY. EVER!"
>The Mega Disharmony Tank disassembles itself, the ponies extricating themselves from their weapons.
>You can hear Rainbow complaining to Applejack about how she never got to use her Super Sticky Cloud Cannon, with Applejack retorting she never got to use her function either, but how she's not complaining.
>Slowly switching from action theater mode to party mode, everyone gets back into the celebration.
>Both you and Celestia get hugs for playing along, and at the end of the day, isn't that all that matters.
>Making family happy, even if that family is a pair of over 1000 year old magical technicolor ponies.