As the Cake Twins were setting out on their journey, Dr. Whooves and Derpy were both strolling through the streets of Ponyville, enjoying each other’s company. Derpy fluttered by and yawned, “I feel better that your parents took Ditzy for the week. But honestly, what do you want to do now that we don’t have the kid to worry about?”
Dr. Whooves just waved his mane and responded promptly. “You don’t think that I have things planned? Trust me, I have us on a perfect schedule for our week off.”
Derpy giggled as she fluttered by her partner. “Well, I have to admit that I usually don’t follow schedules. I rather just go around Ponyville and try new things. I’ve got my job as a mail carrier to keep me content.”
The mare’s husband looked at her and scoffed lightly. “Seriously? We can’t just wander the streets of Ponyville aimlessly! We need to have a plan, so everything runs smoothly!”
Derpy snickered and placed a hoof on her husband’s shoulder. “Dear when does anything in your life runs smoothly? Don’t act like I don’t know what you really do for a living.”
The doctor couldn’t help but blush as he asked. “So, you know that I can travel through both space and time? I thought I had convinced everypony that was just a myth.”
Derpy giggled. “Don’t worry, I won’t tell. But you’ve got a lot of explaining to do, Mister Scientist.”
The stallion just waved a hoof and casually replied. “All in good time. For now let’s just focus on getting to Sugarcube Corner, ok. I’m starving!”
Derpy gave a nod as she continued to fly alongside her husband, as they came upon two unfamiliar ponies running through the streets. One was a large, tan coated pegasus bouncing around and asking for help among other ponies that were walking down the streets. While the unicorn mare was pleading desperately for help.
Derpy and Dr. Whooves both gave each other nervous looks before they ran over to the two odd ponies, not one to ignore a cry for help.
Pound Cake instantly recognized the two ponies, having seen them a lot at his parents; shop and he stomped over as he hugged Dr. Whooves. “Doctor! Thank goodness we found you!”
The Doctor squeaked as he was thrown back and into the dirt as he gasped. “Get off!”
Pound Cake stepped off the stallion and whispered. “Me sorry, Doctor. Me got a little over excited.”
The other earth pony heaved as he got up and responded. “It’s alright. Now please tell me, who are you? You look oddly familiar.”
Pumpkin Cake meekly trotted forward with her head bowed as she whispered. “We Pound and Pumpkin Cake. We big ponies and we need help.”
Both Derpy and Dr. Whooves blinked and paused for a few moments before the two burst into fits of laughter. The doctor got up and wiped the tears from his eyes. “Wow, that’s a good one! Pound and Pumpkin Cake?! To be honest, you two do look like them. But who are you, really?”
Pound and Pumpkin Cake both gave each other questionable looks and Pumpkin was the first to turn around and replied. “But we are Pound and Pumpkin Cake, seriously!”
Pound came over and pleaded. “Yeah, we really needs your help! Mommy and Daddy left us with Auntie Pinkie Pie, but then some magic muffins turned us into big ponies and Pinkie Pie into a baby! But we no know how to be big ponies!”
Derpy fluttered over, gave the two a long look, and gasped upon seeing the resemblances couldn’t be just a coincidence! “Honey, I think they’re telling the truth! They don’t even have their cutie marks! That’s not something that just happens!”
Dr. Whooves gazed at the two nervous ponies and squeaked out loud. “Seriously?! Grown-up foals?! How could this happen?! It’s scientifically impossible!”
Pumpkin began to throw a little temper tantrum as she whined. “Why you no hear my brother?! We transformed into this by some magic muffins! Now come over to Sugarcube Corner and help us! We no can take of Pinkie Pie by ourselves! We not know the first thing about baking or taking care of a baby pony. Heck, we not even sure we can use the big potty. It too scary!”
The doctor turned to his wife. “Well, dear, it looks like our date has to be cut short for now. We need foal items for Pinkie Pie, and it looks like adult diapers for the older foals, just in case.”
Derpy saluted. “Right, I’m on it! I know the stores of Ponyville like the back of my hoof!” She flew off to go grab the foal items, as Dr. Whooves turned towards the twins and instructed. “You two come with me! We can’t have you leaving a mess on the streets! It’s not sanitary, and there’s no flowers or plants for you to fertilize.”
The twins both gave nervous nods as they followed Dr. Whooves towards Sugarcube Corner. Hopefully, this grown-up and his wife could help them.
Dr. Whooves couldn’t believe his own eyes as he entered what had been the twins’ nursery and gasped upon seeing the baby Pinkie Pie fast asleep in the twins’ crib. He then turned towards the two grown-up baby ponies in front of him and whispered (so as not to wake the regressed Pinkie). “So you were telling the truth. Somehow, Pinkie Pie was transformed into a baby and you two turned into adults. Never have I seen such a thing before,” They then all quietly left the room and went downstairs. There, Dr. Whooves stroked his chin and whispered, “Well, there’s only one thing we can do from here, we need to tell Twilight!”
But the twins immediately shouted. “No! No, tell Twily!”
Dr. Whooves looked up with a surprised expression and asked. “Whyever not?”
Pound Cake whimpered. “Well...wouldn't Auntie Pinkie Pie get in trouble for feeding us muffins? We dun wanna get her in trouble!”
Pumpkin Cake nodded. “Yeah! Please don’t tell Twily! It not Pinkie Pie fault!”
But Dr. Whooves just chuckled. “Oh, don’t worry. I’m sure Twilight will understand. Besides, this isn’t the first time she has had to deal with a pony being regressed into a foal. Haven’t you been hearing about all these other ponies turning into foals?”
Before the twins could reply, they heard a knock on the door. And who should enter but Derpy with a bag of diapers and various foal items for both little and big ponies, along with Twilight Sparkle herself?
Derpy looked up with a smile on her face. “Look who I found while I was out!”
The twins groaned as the unicorn stomped into Sugarcube Corner quite angrily and growled. “I cannot believe another pony was turned into a diapered foal! Seriously, I thought we’d stopped this! Now it’s not only turning grown ponies into foals but foals into grown ponies! This is getting ridiculous!” The twins were a bit nervous as Twilight looked over the adults that were once foals and asked. “So, I was told you two are the Cake Twins all grown up?”
Pound Cake gave a whimper as he nodded. Twilight was now a bit curious as she looked at the twins over and whispered. “Wow, it's really cool to see you two grown up like this. You even know how to talk. Oh, if only I’d thought to bring ink and parchment with me.”
Pumpkin was nervous as she asked. “Yes, um thanks, Twily. But you can turn us back into babies, right?”
Twilight came over to the magic muffins that had been left out and sighed. “Maybe eventually. These muffins are what triggered the transformation. I’ll have to look over them and see what I can do. Until then...I think it’ll be best if Dr. Whooves and Derpy stay here to look after things.” Both of the Cake twins sighed in relief as Derpy, and the doctor both groaned.
Twilight blushed and apologized to them. “I’m sorry, but we can’t have two full-grown babies running around Ponyville unsupervised. Not to mention Pinkie Pie is a foal now, she obviously can’t be trusted to keep them in line.” The unicorn shivered as the thought of Pinkie Pie as a baby running around Ponyville, diapering ponies and throwing foal powder everywhere while shouting “Diapee pawty!” came into her mind. She shivered in fear and whispered. ”I can only imagine how she’s going to be as a foal. Somepony needs to keep her under control as well. Otherwise, she’ll surely make a mess. In more ways than one, probably.”
Both Dr. Whooves and Derpy both gulped as their ears went behind the back of their heads. Then Twilight tried to reassure them. “But it’ll only be for a day or two. I’m sure I can come up with a cure or something by then. Besides, maybe this time the regression will wear off eventually, and everything will go back to normal.”
Twilight then quickly sped out of the cafe, leaving the other ponies with looks of uncertainty. The quiet was broken when Derpy held out the diaper bag. “Well, I guess it’s time to diaper you two up. Can’t have you leaving puddles on the floor.”
Both Pound and Pumpkin were now blushing, looking down at the biggest and thickest diapers the two had ever seen. The padding seemed to rise up like massive pillows of poof now securely taped around their rumps. Walking had appeared hard before, but walking around with their new undergarments looked like it would be a chore. Still, at least they wouldn’t have any more accidents to clean up, so that was a relief.
Derpy was looking down at her handy work and scrunching the diapers with a hoof, checking to determine if she did it right. “Hmm, I think I need to adjust the straps, they're a bit lopsided. Hold still, you two.” The two big foals groaned as Derpy went about adjusting the diaper straps, while Pound and Pumpkin gave each other confused looks.
Derpy then helped both ponies up as Dr. Whooves was coming downstairs and proclaimed. “I stored all the extra foal supplies in the nursery, and thank Celestia Pinkie Pie is still asleep in her crib.” He came down the steps and nearly doubled over in laughter upon seeing the two big foals with their diapers looking lopsided.
Derpy sighed and asked. “Honey, can you help? I never had to diaper foals this big before. Dinky had outgrown her diapers by the time she was three, and even then you were usually the one changing her.”
The stallion trotted over and helped fix the tabs around the foals waist as he cooed. “Oh, don't worry, Derpy. You did a pretty good job. It has been a while since either of us has touched a diaper, of course, we’re going to be rusty the first time getting back into it.” He then took each foal by the hoof and helped them up on all fours.
The twins looked around with deep blushes, seeing the massive diapers behind them poofing outwards and spreading their legs apart far more than their diapers had when they were just foals. Dr. Whooves then replied. “Now, while Pinkie is napping, how about you two play downstairs? I'll find some toys for you.”
The two adults looked at each other as Pound Cake commented. ”Well...I think Mommy and Daddy want to have the shop running, so they make money.”
Pumpkin nodded. ”Yeah, if it open not then they gonna run out of money! Then we won’t have enough money for diapees! And it is all our faults!”
They both began to whimper as Depry fluttered over, gave each adult sized foal a pat on the head, and cooed in a reassuring tone. “Oh, don’t worry about that. Sugarcube Corner doesn’t need to run every day, you two will be just fine. We only need to keep it closed for a day or two until Twilight finds the cure.”
But Dr. Whooves stroked his chin. “Not really. I think we wouldn’t want to have to Mr. and Mrs. Cake know about this, or it could cause them to panic. To keep up appearances while Twilight is making a cure, we should run Sugarcube Corner as they would, in addition to taking care of the foals.”
Derpy put her paws on her hips and asked. “How do you think we should do that? We don’t know anything about baking, not to mention we have two big babies and one small, crazy baby to care for. We’re not miracle workers.”
Dr. Whooves adjusted his bowtie as he explained. “Well, it’s not like we don’t have experience caring for foals. We raised one of our own after all, and I can use my genius to make a machine to bake for us. As for our two big babies…” He tapped a hoof to the chin as he pondered. “I think we can pull it off saying they’re distant cousins of Mr. and Mrs. Cake who are incontinent. If anypony asks, we’ll tell them that Fluttershy took the twins to her cottage because Pinkie Pie is sick with the horsey hives, which is why these distant cousins came to help us.”
Pound Cake blushed. “But we dun know about being big ponies. We no know how to act or talk like them.”
Dr. Whooves came over. “Well, for today I can teach you two how to be big ponies a little. Maybe even help you learn how to use the potty enough to where you won’t need diapers, and we won’t need the incontinence part of the cover story,” He then looked down at their diapered rump and sighed. “But first, you two need some clothes…” He turned to Derpy and asked. “Would you mind watching Pinkie Pie while I’m taking care of these two?”
Derpy gave a nod as she smiled. “Sure, that’s fine,” She then came over and chirped. “Was this a part of your plans?”
Dr. Whooves blushed as he led the Cake Twins upstairs.
The two were now in their parents’ upstairs bedroom, as Dr. Whooves was helping the two into their new outfits.
Pound Cake now wore a thick, white apron and a chef’s hat that sat upon his head, while Pumpkin Cake wore a cute, light blue apron tied around her waist. Both blushed to see their diapers poking out the back as Dr. Whooves clapped his hooves. “Wonderful, you two look amazing! Now, I need to know if you can get some basic things down into your little foal minds,” They both turned around and looked over as Dr. Whooves explained. “You two look presentable for now. But you two need to sell two major things about being adults. First of all, look up and present yourself. “
The two then stood up straight, looking up proudly as Dr. Whooves walked around the two ponies and pressed a hoof into their diapers, hearing them crinkle “Now, walk just like this,” He strode through the room with his head in the air and walked around the room as he turned back to the two. “Now you try.”
The two ponies did their best, but the thick diapers made them have a big, adorable, and noticeable waddle. The diapers are crinkling and shaking back and forth. Afterward, Dr. Whooves clapped his hooves. “That was pretty good, you two are naturals,” The two beamed smiles of pride as Dr. Whooves came forward. “Now, you two don’t need to worry about baking as that’s way too complicated. Same goes with dealing with the cash register. All you two should do is help serve the customers their food.”
Pound and Pumpkin both smiled as he then took two silver platters with straps attached to them, and placed one on Pound Cake’s back and one on Pumpkin Cake’s back. The stallion then set blocks on their back platters and explained. “Now, I know you two don’t have a lot of balance, so I strapped them onto your backs,” The stallion then sat down in a small chair with a small table and instructed. “Now then, please serve me the fake foods.”
Pound and Pumpkin gave each other nervous looks as they then proceeded over. Pumpkin grunted as she used her magic to place her blocks on Dr. Whooves’ plate. But Pound tried using his wing and squeaked as he stumbled, backward falling on his padded rump with a loud plumph! The big, plump stallion squeaked and cried. “I sowwy!”
Pumpkin Cake smirked as she threw back her head and laughed. “Ha! I am less clumsy than you!
Pound Cake kicked about, making his diaper crinkle quite loudly as he whined. “Tat not fair! She has magic, and I dun. She cheating!” He threw his forehooves over his chest and grumbled.
Dr. Whooves sighed. “That’s okay, Pound Cake. Maybe you can’t serve food, but I have another important job for you,” He helped the stallion up onto his hooves and fixed his apron, then proceeded over to the diaper and fixed it with his magic as he asked. “How about you instead go and greet ponies as they come through the door or leave?”
Pound Cake eyed Dr. Whooves as the stallion went to the door of the nursery, opened it, and explained. “Now, you hold the door while I walk through, and you simply say good day.”
Pound Cake then waddled over to the door and held it as he turned towards Dr. Whooves who went through the doorway. The big foal bowed and stammered. “Go...good day, sir!”
Dr. Whooves gave a nod of approval. “Very good! I think we have your jobs!” The two beamed smiles of pride as he added. “Now then, we also need you two to have new names, so ponies don’t get suspicious,” The twins both blushed as Dr. Whooves smirked. “Pumpkin, I think you will be Spice Cake from now, and Pound you will be called Cream Cake.”
They both looked at each other and shrugged as Pumpkin asked. “Are you sure it a good idea to lie to ponies?”
Dr. Whooves replied. “Well, yes. I know it seems bad, but most ponies think the age regression epidemic is over. We don’t want to cause a panic. But we must not let Pinkie Pie downstairs, she’s too recognizable. She’ll blow our cover story completely.”
They both shrugged, and Pound Cake commented somewhat nervously. “Bu..we still dun know much else about being adults. Are you sure tat's all we needs to know?”
Dr. Whooves gave a nod. “Of course I'm sure. Twilight will undoubtedly have a cure in a day or two so that should be good enough. We can worry about more optional things later. Now, how about you practice your jobs while I make a machine to bake the goods?”
The two twins chirped. “Okay, Docta!”
Dr. Whooves blushed and quickly went back downstairs as Pumpkin Cake exclaimed. “I gonna practice serving ponies!”
Pound Cake whined. ”Yeah?! Well, I gonna practice letting ponies through a door! I’ll do it better than ya do ya job!” He humphed as he opened the door and practiced chirping. “Have a nice day!” While Pumpkin looked around to see a doll and placed her on one of the chairs. The mare then continued to practice her adorable diaper waddle, while making sure to serve her blocks on the platter to the doll.
Meanwhile, Derpy had taken baby Pinkie Pie downstairs. Pinkie was babbling incoherently as Derpy opened up to the kitchen to see a giant cylinder-shaped robot with mechanical arms. Derpy slowly walked up to her husband and cooed. “Hey, Pinkie Pie is up.”
Dr. Whooves pulled out from under his giant robot and blushed. “Sorry, did I wake her?”
Derpy shook her head. “No she was getting fussy he messed her diaper, and I had to change the poor dear.” The mare then placed Pinkie down as she trotted over towards Dr.whooves in her thick diaper with an adorable waddle. Dr. Whooves dawwed. “Oh, she reminds me of when Dinky was a baby!”
Pinkie Pie giggled. “I dun know about tat! But I am pweety cute, I bet!!”
Dr. Whooves smirked. “Don’t let it go to your head, missy.”
Pinkie Pie looked up at Dr. Whooves and gave him a questionable look as she babbled, “How can ya undewstand foaw babble? Nopony can do tat!”
Dr. Whooves smirked. “I've been studying the language of foals for years. It’s actually quite advanced, it’s not just goo-goos and gaa gaas.” The two continued their conversation as Depry watched with a surprised expression on her face hearing both Pinkie Pie and her husband speaking in foal babble.
Afterward, Pinkie then waddled over to the doctor's toolbox and exclaimed. “Weww, ya maybe a supew smawt pony but ya wong about one ting, I'm cwaziew ten Dinky Whooves, watch!” She then took a hoofful of nuts and bolts, shoved them into her diaper and started to dance around, throwing the metal pieces all over. The Doctor and Derpy squeaked and burst into laughter.
Dr. Whooves quickly took Pinkie Pie into his hooves. “Yeah, I'm betting you’re going to be one heck of a trouble maker. Now I have a few questions for you.”
Pinkie giggled as she kicked about, making the metal clink in her thick diaper and she asked. “What is it?”
Dr. Whooves continued. “Well, I want to know if Mr. and Mrs. Cake left any special instructions?”
Pinkie paused as she remembered that Mr. and Mrs.Cake said they wanted to keep the shop closed while they were gone. But, she saw Pound and Pumpkin Cake having so much fun getting ready to run the shop. So she shook her head and babbled. “Nope, just the usuaw stuff about keeping the foaws safe. tat's aww.”
Derpy was unable to hear a word the two were saying and came over and asked. “So what did you two discuss?”
Dr. Whooves chuckled as he nuzzled her, making the little filly gurgle and coo as he replied. “Oh, nothing. I was just making sure she was okay. She also mentioned that Pound and Pumpkin are still practicing being adults, right?”
Derpy gave a nod. “That's right, the other foals have been practicing all evening. I think I’ll make something for dinner for the hungry babies, then get them to bed soon.”
Dr. Whooves sighed as he placed Pinkie down and let her suck on a pacifier “I’m sorry this whole thing ruined our date. I was hoping we would have some alone time.”
Derpy came over, picked Pinkie back up, and gave her a boop on the nose as she placed the foal on her back. “Oh stop it! You know how long it’s been since I last changed Dinky’s diapers! I'm going to have a great time.”
Dr. Whooves chuckled. “I love your optimistic attitude.”
Derpy scoffed. “Oh please, you need just to stop being a pessimist.”
Pinkie’s tummy made a loud growl as she placed her hooves over her belly and scrunched the diaper between her legs making the padding crinkle. Derpy dawwed and cooed. “I’m going to go feed the babies. Good luck on your project honey.”
Dr. Whooves nodded and replied. “You should check her diaper for screws and nuts first. She put a whole bunch into her diaper,” He added. “I should probably invent something so you can understand her, in case she needs something, and I’m not there.”
Derpy blushed and nodded. “Right, I'll give the little Pinkie a diaper change. You work on your inventions.” She then carried the baby Pinkie Pie away who was blushing as she nuzzled into Derpy's mane and squealed. “Being a baby is great! I can do whatever I want and get away with it! I can have fun all day long, and nopony can stop me! I just hope Twilight doesn't find a cure too soon! I’m gonna get to have some fun!”