Mango spent several hours flying towards Canterlot Castle with Fluttershy and her daughter Echo sitting behind her. The bat pony mare was exhausted from flying dozens of miles to and from Canterlot.
They finally arrived at the castle with two little foals on Mango's back. They were both also looking somewhat exhausted (having skipped their naps and spent most of the evening running around). Mango eventually landed outside the castle; she laid her foals down, turned towards her daughter, and growled. "Now, Echo, you will be on your best behavior while you're here. Or you'll be grounded for a month."
"A month?!" The filly whined.
"Yes, that's right. I won't have any of your antics while we're meeting with Princess Luna, is that understood?" Mango sternly replied. "You stay with me and don't go wandering off on your own no matter what. If you need anything: A change, a snack, the potty, let me know."
"Otay, Mama." The little filly mumbled as she bent her head downward.
Mango then adjusted Fluttershy on her back as the three continued through the halls. They eventually made their way to Princess Luna's bedroom, where they found two batpony guards outside.
"Commander Mango, you're back already?!" One of the guards asked in surprise.
"Yes, I want this matter resolved by finding out who this little one is." The mare explained with an exhausted sigh as she was still recovering from all the flying she had done.
The two guards looked over at the little filly on her back and dawwed. "Aww, she's adorable!"
Fluttershy, feeling self-conscious, threw her wings over her eyes. But it only made the guards daww even more.
"Well, as much as I would love to coo over this cutie, we should make sure she isn't an adult who was regressed," Mango explained.
The guards nodded as they opened the doors. Mango went trotting inside to find Princess Luna standing by a mirror, seemingly getting ready to perform her duties for the evening.
Princess Luna turned toward them with a smile. "Oh, Mango, it's so good to see you!"
"Yes, princess. As requested, I came with the foal you suspect to be Fluttershy." Echo abruptly responded.
Luna then picked up the little baby bat pony in her magic and had her come close to her. She nuzzled the little one with her muzzle and cooed. "Oh, this is the little cutie you were talking about." She then looked at the foal rather thoroughly and gave her diaper a few loving pats. The princess of the night wasn't entirely sure if the foal was Mango's, seeing how shy she was, throwing her batwings over her eyes.
The princess of the night recognized Fluttershy almost immediately as she snickered. "Aww, she's so cute! Yes, I would say I'm ninety-nine percent sure that this is indeed Fluttershy." She then placed Fluttershy down and wrote a letter to Twilight about how her friend might have been turned into a baby bat pony. Her assistance was required in turning Fluttershy back into an adult pegasus.
Princess Luna then lit her horn and sent the letter to Spike as she turned her attention to Mango and asked, "When Twilight responds, she'll surely come by to turn the little one back to normal. In the meantime, would you like to stay at the palace for the day?"
"Yes, that would be great; my wings are killing me!" Mango replied with a sigh of relief.
Meanwhile, Luna started to play with Fluttershy a little bit, tickling her belly with a wing and making Fluttershy kick and coo. She reached out and began to suckle on one of Luna's hooves, making the princess and Mango daww.
Luna let Fluttershy suckle on her hoof for a bit and then hoofed her to Mango. That was when she noticed little teeth marks over her ankle.
"Oh dear, it looks like the little one bit you," Mango commented.
The princess of the night inspected her hoof and just gave a chuckle as she said. "It's fine; she didn't break the skin. As a snack, I had a few fruit tarts, so she was probably just sucking on some leftover tart jam on my hooves."
"Even so, I do apologize for that. I know I raised Echo to be better than that. I should've made sure Fluttershy knew not to do it either." Mango yawned. She then trotted off with the foals and was led by Princess Luna to a spare bedroom. The bat pony was rather impressed to see the room was rather big and even had a fully stocked changing table.
Princess Luna then smiled. "I hope this is all to your liking."
Mango bowed her head. "This is more than gracious, your majesty. Thank you for allowing me and my foals to stay here as a guest."
"It's no problem at all. Have a good day, and sleep well," Princess Luna yawned as she closed the door behind her.
As soon as the princess did so, little Echo turned to her mother and said. "See, Mama? I behaved! I not grounded, am I?"
"No, you're not, you were a very good filly, and now it's time for bed. So come on, let's get you to the potty, so you don't have an accident. Just be careful not to fall in again." Mango yawned once more, and she escorted her daughter to the bathroom.
"I not," Echo replied as she was brought before the toilet and pulled down her diaper.
A short time later, after getting her daughter ready for bed, Mango wrapped her tail around a banister. She held her foal within the folds of her wings as Echo clung to her. It wasn't long until they were comfortable and fell fast asleep.
Luna rubbed her hoof full of drool, chuckling as she thought about how Fluttershy was rather adorable as a baby bat pony, for however long she would stay that way. The princess of the night stretched her wings and then trotted over to the mirror as she was getting ready for her duties. But then she noticed that her body started to shrink in size, her growing hair outward, and her teeth became pointy. It wasn't long until she was reduced to a foal.
Having been regressed once before, Luna knew rather quickly she was a foal again. She quickly ran over to a mirror and gasped upon seeing her reflection! There, staring back at her, was an adorable little baby bat pony with two small and leathery bat wings where her once feathery wings had been. Her teeth were now tiny fangs. This wasn't just any old age regression; the princess of the night had turned into a bat pony as well!
Luna waddled to her door, hoping to find some pony to help her out. The little filly pounded her tiny hooves on the door while crying! "Somepony help! I got turned into a baby again!"
Eventually, the door opened, and two of her batpony guards entered. Looking around, one looked down at the little foal. Then he bent down and picked her up. "Oh my! Where are your parents, sweetie? Are you lost?"
But the other guard looked around the room, and that's when he realized that the baby was Princess Luna and started to freak out! "What the heck is going on here?! Where's the princess?!"
The soldier holding the foal looked closely at her and started to see that the colt resembled Princess Luna quite a bit. "I think Princess Luna has turned into a baby again!"
Princess Luna just pouted at the guards and snapped. "Seriously?! Can't ya understand me?! Just take me to my sister! She can get with Twilight and turn me back to normal!"
The guard holding Luna just gave her a confused look as he stammered, "I…I think she's trying to tell us something."
"Yeah, I thought regressed adults could still talk?" The other guard asked while scratching the back of his head with a hoof.
Luna got so frustrated as the guards seemed to have stopped listening to her, and she went and bit one of the guards with her teeth.
"Ouch! Hey, Princess Luna, don't do that!" The first guard exclaimed as Luna began to suckle on his hoof. The guard then slowly regressed into a foal as well, with his armor collapsing over him as his partner started to burst out laughing. His comrade pouted and snapped. "Whatcha laughing at?!"
The older soldier burst into even more laughter. "Aww, I can't hear you. Can you say Da-Da?"
The other foal got rather frustrated as he pounced on and bit the older pony. It wasn't long until the adult pony slowly regressed into a baby bat pony!
The two guards started fighting, flapping their wings and slapping each other. That is until Luna raised her wings and shouted. "Ya two, stop tis right now!"
"Yes, Princess Luna." The other two guards mumbled as they lowered their heads.
Luna gave an exasperated sigh before looking around the halls as she said. "Otay, let's go find my sister. She ta only one who can help us. But before we go, you must remember not to bite anypony."
"Ya bite us first!" One of the guards snapped back.
"Yeah!" The other guard shouted as well.
Luna just sat back with a cute pout. "Well, ya wasn't listening ta me! I can't stay a baby, I got my royal duties, and ya probably dun wana to stay as babies either. So we need to find my sister, or we'll stay like this."
"Yes, Princess Luna." The other foals chimed in.
"Otay wets go!" Luna replied and then had the other foals follow her down the hall, hoping they could find Celestia fast! Right now, the only pony that could turn them back to normal was Twilight, and she was all the way in Ponyville. So they'd have to contact Princess Celestia and have her send a message to Twilight.
The trio of foals eventually came to Princess Celestia's room and managed to open it. Then they came to Princess Celestia as she was going over some paperwork at her desk.
Celestia then turned to see her sister and the baby guards. She put a hoof over her mouth upon seeing how adorable they looked and gasped, not appearing to recognize them! "Oh my! Where did you cuties come from?!"
Luna tried to explain, babbling gibberish at her sister, but this made Princess Celestia daww as she levitated the babies into her lap and started to nuzzle them. Celestia then looked downward. "Oh my, you all need diapers! We don't need you leaving puddles all over the castle grounds. I don't know if any of you are potty trained," She then levitated three diapers over along with a container of foal powder and commented. "Lucky for you, I've been stocked with foal supplies just in case more ponies got regressed."
Luna got more frustrated, kicking and whining upon seeing her sister not listening to her. But Celestia quickly plopped a pacifier into Luna's mouth and chirped. "That's enough, sweetheart. We need to get your diaper on before you make a mess." The princess then laid the foals down on the ground. She then went about powdering their flanks and then strapping the foals up in fresh protection. Princess Celestia then made cute "baby talk" with the foals as she finished taping the diapers up, making sure they were snug.
But all of this "babying" made Luna and the other regressed ponies even fussier.
"Well, seeing as you're all bat ponies, I believe that you must be some lost foals belong to one of my sister's nightguards," Celestia I should investigate to see who your parents are…or if you're regressed, adults."
Luna groaned, rubbing down her face. Her sister was genuine, and she did appreciate her going out to help some lost baby bat ponies. But the truth was it would take forever for her sister to go talk to every bat pony guard under her employment. It could be a full day before they were back to normal, and Lina wanted to be out of diapers as soon as possible. Out of frustration, she shouted! "We dun have time for tis!"
As Celestia was going to leave her room, the princess of the night bit her sister on the hoof, and it wasn't long until the princess, too, was regressed in a cute baby bat pony. She had these pointy fluffy, white ears and cute little pointed teeth. The princess turned towards her sister and asked, "Did ya turn me into a baby bat pony?!"
Luna rolled her eyes and snapped. "Well, ya wasn't listening ta me! I had no other choice!"
"Well, I'm sowwie for that, but why did ya turn me into a baby again?!" Celestia shouted. She then looked over at the other foals and asked. "Also, who are all of you?"
The two colts went to attention, looking rather adorable with their padded flanks stuck out as they proclaimed together. "We royal nightguards!"
The filly pointed to herself and shouted. "I'm ya, sissy Luna! I've been trying to tell ya I was a baby, and we need help getting back ta normal! We dun wanna be in diapees!"
Celestia stuck her tongue out and jeered. "Well, sister, now that ya turned me into a foal, we're both babies again. So we gotta find Twilight to change us back to normal."
"Right! But …how? We can't talk to grown-up ponies; they all think we just saying baby babble!" Luna whined, now feeling rather bad at turning her sister into a baby.
"Wait, big ponies can't understand us?" Celestia asked, being somewhat concerned.
"No, tey can't. Ya couldn't understand me even when I was shouting at you!" Luna admitted, making Celestia slam a hoof to her face and groan. She then heard her tummy growl. "Otay, first I need a diapee. Ten wets get something ta eat, and after that, we can figure tis out."
"Oh yeah, I gonna diapee ya! Now I get to be the big sister!" Luna giggled as she rushed over to her sister's closet before bringing out a diaper.
The princess of the sun put a hoof to her face as she was somewhat reluctant to go back to wearing diapers and babbled. "Can't believe I got put back into diapees twice!"
"Hey, some would say you're lucky." Luna snickered as she assisted her sister in laying down and having a fresh diaper strapped over her flank. After Celestia had a fresh diaper, the foals headed towards the kitchen to find something to eat.
Fluttershy threw her hooves in the air as she slowly got up, and she turned to see Echo was fast asleep. But what was weirder was that she was now on the ground and was surprised to see that Mango was now a chubby, baby bat pony. Fluttershy gasped and crawled backward, surprised and worried, seeing that Mango was regressed. Who did this?! What happened?! She then turned to see that it was still night outside, and the sun had yet to rise. That meant something was wrong, and she had a sinking feeling that princesses were regressed.
"Mama, ya a baby!" Echo cried as she turned to see that Mango was also waking up.
Mango was surprised to see herself in her regressed state and started to freak out and cry! "Na, no, no! How did I turn into a baby?!"
"I dun know, but now I ta oldest! And ya gots ta listen ta me!” Echo giggled as she clapped her hooves.
"Ya stop, young lady, I still ya, mama!" Mango snapped as she got up, blushing as she waddled over to the changing table and pulled out a diaper.
"Oh, let me help!" Echo squealed, rushing over to help tape her mother in a fresh diaper.
After that, Echo went off to use the potty (again, seeing as she had gone earlier before bed) as Mango waddled over to Fluttershy and gave her diaper a pat, seeing that it was soggy. "Come on. I may be a foal, but I still know how to change a diapee."
Fluttershy simply nodded and let Mango go about changing her diaper. Mango was much clumsier, but she was still knowledgeable, wiping Fluttershy down, powdering her flank, and then making sure the new diaper was snug around the filly's waist. After the change, they all gathered up as Mango mumbled. "How did I turn into a foal?"
Echo bowed her head and mumbled. I dun know how ya became a foal. But I tink if you're a foal, maybe others might be one too!"
Mango nodded as she waddled around, her cheeks flushing red as she got used to the fresh padding around her flank. "Yeah, ya right. We gotta see who else got turned into a baby bat pony." She then led the other foals out of her room (lucky enough for them that their door was slightly ajar, allowing them to get out of their room).
Meanwhile, Fluttershy vaguely remembered suckling on Mango's hoof last night. And she wondered if maybe she had turned Mango into a foal?
The foals continued through the castle and saw that dozens of ponies all over the place were now baby bat ponies, flying around and chasing each other. "How did tis happen!?" Mango shouted again, somewhat confused.
They eventually made their way to the kitchen, where they found a pantry full of fruits of all kinds: Strawberries, mangos, apples, and blueberries. All other fruits were now husks as the baby bat ponies were sucking them dry. They then found the princesses in their baby batpony forms.
Luna turned towards them and shouted. "Hey, Mango! How are ya doing?"
"Obviously not good! What is going on here?!" Mango shouted, surprised to see so many bat ponies flying about.
Luna looked somewhat embarrassed as she said. "I'm sowwie, but I was hungry and came down here..and…well…I accidentally bit a guard for being rude to me. He wasn't listening ta me!"
"Not my fault! I couldn't understand ya!" The other guard shouted.
"Yeah. Then she bit me." Celestia chimed in.
Luna stuck her tongue out at her sister and babbled, "Ten ya bit a noble who was annoying ya!"
"Well, ya bit my other guards! Ya, just a little biter!" Celestia snapped back.
"They was gonna stop us, what else was I gonna do?!" Luna whined. The two continued to bicker for some time before the princess of the night eventually rolled her eyes. "Anyways, we accidentally started turning everypony into baby bat ponies."
Mango slammed a hoof to her face, seeing the foals flying around and causing chaos, "So, what do we do now?"
Luna waddled over and said. "We gotta go find Twilight. She ta only one that can turn us back to normal."
Mango stood up and snapped. "Otay, but that means ya two need to stop biting ponies! We dun need more baby bat ponies running around!"
"Yes, mam." Celestia and Luna chimed together.
Mango then turned to face Fluttershy and added. "That means you too, Fluttershy. It clear ya bite caused me and Princess Luna ta turn into foals."
"Yes, mam." Fluttershy squeaked in embarrassment.
Mango then turned her attention back to Celestia and Luna. "Otay, so we need to find a nursery for these foals. We can't have them running loose! Faust knows if they escape, every fruit in equestria will be sucked dry!"
"Yeah, that would be a big problem," Luna admitted with a blush upon seeing almost all the fruit in their massive pantry was now dried up husks.
"Not only that, all tis juice makes ya pee awot!" Celestia squeaked as she looked down to see her diaper was already yellowed. Soon everypony began bickering amongst each other about what to do and how they would stop the foals from leaving the castle.
Meanwhile, Fluttershy looked rather nervous, feeling somewhat bad at seeing how she was responsible for all of this. But as she looked around the pantry, she noticed a few untouched fruit boxes, and then an idea started forming in her head. "Um, excuse me?" Everypony then turned towards her as she took a few mangos that hadn't been sucked dry and said/"Look, we use tis fruit to lure ta baby bat ponies to a nursery, and we stuff them up. We played with them until tey all tuckered out, and they took a nap; we then made sure tey got diapees on. That way they all sleep and have protection, giving us plenty of time to go find Twily!"
Celestia and Luna blinked, seeing that this was a decent plan, and Mango waddled and hugged Fluttershy and chimed. "Yes, that's a great plan! Ya, so smart Fluttershy!"
The little foal felt rather proud as the princesses chanted, "Fluttershy! Fluttershy!"
"Otay, stop, ya embarrassing me!" Fluttershy squeaked as she threw her wings over her eyes.
Then Echo stood up and said. "Otay, ya and mama should lead! Let's go round up ta baby bat ponies!"
"Yay!" The other foals squealed as they gathered the fruit in the boxes and headed off to get the rest of the baby bat ponies to follow them.