Author's Note

No tiebreaker was needed this time, Cheerilee had enough votes from previous rounds to edge out the competition. Scootabom1 proposed having Cheerilee be mentally regressed to all but babbling, and then playing pretend daycare/preschool. I decided to partially go with that idea, taking a page from the fic this is a continuation of. More specifically the Spike chapter where it was revealed at the end that Spike was only pretending to be mentally regressed.

There have been fewer and fewer votes in recent chapters, so I'm not sure how much longer I can keep this going if I don't get any more votes or ideas. I want to at least try to keep this fic going until either July or August of this year before wrapping it up. Whenever I do decide to end it, anyone will be free to pick up from where this might leave off. I've been specifically crafting something to give me an off ramp if needed.

But as long as I keep getting votes for eligible characters and get ideas to work with, I'll keep this fic going.

Characters ineligable under any circumstances:
Starlight Glimmer
Discord
Trixie
Sunburst
Cutie Mark Crusaders
Flurry Heart
School aged or younger children (i.e. Cake Twins)
Characters introduced after Flurry Heart (Starswirl the Bearded, the Pillars, Star Tracker, Mudbriar, etc.)

Characters that can only be done in group pairings:
Mane six
Spike
Princess Cadence
Shining Armor
Princess Luna
Octavia and Vinyl Scratch
Twilight Velvet
Spitfire (with or without Wonderbolts)
Lightning Dust
Maud Pie (without Mudbriar)
Moondancer
Cheerilee

Characters previously voted on:
Lyra (with Bon Bon) - One and a half votes

Professor Pampers (Cheerilee)

"Good morning, Twily!" Princess Celestia cooed as she nudged her fellow alicorn awake, standing right beside the padded princess' bed with that big, motherly smile.

Twilight immediately reached out her hooves and hugged the sun princess, cooing back in a happy and playful tone. "Good morning, Mommy," She then used her horn to grab Smarty Pants, all the while asking the elder alicorn. "What are we going to do today?"

Celestia's smile grew brighter as she watched Twilight climb out of bed, proudly displaying that padded posture of hers. Even with how long it had been since they'd started this mother/daughter roleplaying, the warm and fuzzy feelings had never faded. It helped that Twilight always looked so cute in her diapers no matter what she did. She then said to the younger princess. "You'll see soon enough, Twily." Then she lit up her horn and pulled her fellow alicorn close.

A blush formed on the padded princess' face as she was subjected to an abrupt and unannounced diaper inspection. "I didn't have an accident, Mommy."

"I'm just making sure, Twily," Princess Celestia said with a knowing wink. "Foals don't always know when they go pee pee or poo poo. And what kind of mommy would I be if I let you get a rash?" She ended the diaper check a moment later, playful patting the padding. "Just as I thought, you're all nice and clean. Good job, Twily."

Twilight beamed with exaggerated pride. "I'm just doing my best to make you happy, Mommy."

The sun princess nodded. "You make me happy no matter what you do, Twily. Whether you use your diapers or the potty, I will always love you just for being you. And I mean that sincerely. Whatever makes you feel happy and safe makes me feel happy." It was possible to detect the faintest hint of worry creeping into her tone of voice, as if she feared that Twilight was perhaps becoming a little too attached.

The padded alicorn smiled back. "I know, Mommy. I know," Then she looked around the room, only for her eyes to notice no sign of anypony besides her and Princess Celestia. That prompted her to ask. "Where's my next playmate, Mommy? You've always brought one with you," She let out a gasp! "Wait a minute, are you going to be my playmate today, Mommy? Just like my other mommy was?"

Celestia snickered and snorted with a goofy grin plastered on her face. "Oh Twily, as much as I would love to join in on the fun with you, I can't. Who would I ever get to watch over you if I stopped being your mommy? The castle staff work hard enough as it is, I very well can't add foalcare to their list of already overwhelming responsibilities," Once she had regained her composure, she simply stated. "But I was able to find somepony willing to play with you. And don't worry, she's in diapers too. In fact, she's already waiting for you down at the dining room. Shall we go?"

Grasping Smarty Pants tightly between her hooves, Twilight gave a firm nod. And thus, with a flick of the horn from Princess Celestia, both alicorns were teleported away.

When Twilight and Princess Celestia arrived in the dining room a moment later, Twilight's eyes immediately fell upon a very familiar earth pony mare with a vivid reddish-pink coat sitting in one of the chairs at the table. She had pale, light grayish-pink locks, and her grayish-green eyes had that sort of far away look to them. And the cutie mark of three smiling flowers poking through the diaper left little doubt as to the mare's identity.

"Is that Cheerilee?!" Twilight let out a gasp! She was more surprised by how... infantile the earth pony seemed to be acting, given that she was pounding her hooves on the dining room table and appeared to be babbling incoherently. It was even possible to see a faint bit of drool coming out of her mouth.

Princess Celestia chuckled ever so softly, and put a hoof to her mouth to try to suppress the giggles. "No, Twily, that is Professor Pampers. That's what she insists on being called."

"Professor Pampers?" The padded princess blinked in surprise as she nevertheless made her way over to her new playmate.

When Cheerilee saw Twilight approach and heard the princess call her by her chosen nickname, the earth pony mare lifted a hoof up from the table and sat up absolutely straight. It was almost like she was coming out of a trance of some sort. "Yes, that's me," She giggled as she swished her tail. "I'm Professor Pampers! I have a PHD in diaperology!"

"Really?" Twilight blinked anew.

Cheerilee's giggles grew louder. "Of course not! Don't be silly! There's no such thing as diaperology! I just made that up because that's something a foal would say."

The padded alicorn was most surprised to hear Cheerilee talking normally, whereas a moment before she had been babbling and drooling.

The off-duty teacher seemed to sense what Twilight was thinking, for she explained. "I know what you must be thinking. I'm not mentally regressed. I still have my adult mind. But I'm trying my best to act more like a foal and less like an adult, hence why I'm calling myself Professor Pampers," She paused and poked at her padding with a hoof, delighting in how it crinkled and compressed. "I figured that if I'm going to teach classes on foalcare and on parenting, I should get some hooves on experience with the mindset of a foal. Studies have shown that it's very fascinating. And when Princess Celestia offered me a chance to study it personally... well, how could I refuse?"

"So you're just pretending to be a foal?" Smarty Pants suddenly spoke up.

Cheerilee nodded, greeting the stuffed animal. "Oh, hello there, Smarty Pants. I was wondering when Twily was gonna introduce me to you. And yes, I'm pretending to be a foal in both body and mind. I'm not very good at talking like a foal, though. So I'm mostly just going to babble and make noises. I'm here to learn, after all." Seconds after saying that, she went back to drooling and babbling, sounding rather convincing as she did so.

Princess Celestia came trotting over, explaining to Twilight. "I did offer her the chance to be mentally regressed, but she said it would be better if she stayed an adult and just pretended to be regressed. I know you'll teach her well, Twily. Just make sure you don't take advantage of that and get her into trouble," Her tone of voice took on a slightly sterner tone as she added. "Don't forget, I can punish you the way a mommy would if you act up."

Twilight shuddered, briefly remembering what had happened the last time she had experienced such punishment from the sun princess. The physical pain to her rump might have healed, but the memories still lingered in her mind. "I'll be good, Mommy," She firmly insisted. "And so will Smarty Pants. We won't do anything with Professor Pampers that we're not supposed to. Right, Smarty Pants?"

"Right, Twily," Smarty Pants replied. "We'll be the best behaved foals ever!"

The elder alicorn's smile returned as she clapped her hooves together in approval. "Good!" Then with a coo she declared. "So can I trust you to stay put and keep an eye on Professor Pampers while I fetch breakfast?"

Twilight firmly nodded. "Uh-huh." She proceeded to waddle over, sitting down in a seat next to Cheerilee and having Smarty Pants sit in the chair next to the alicorn.

Celestia, satisfied with the response, trotted out of the dining room and into the kitchen, soon disappearing from sight.

Now alone with Cheerilee, the padded princess watched as the earth pony mare pretending to be mentally regressed started putting a hoof into her mouth and sucking on it. Immediately, Twilight lit up her horn and pulled the hoof out, scolding her playmate. "Mommy says we're not allowed to suck on our hooves, especially not before eating. And Mommy is always right."

Cheerilee babbled and cooed, but seemed to understand what was being said. It was amazing how quickly she was getting "into character". It was almost as if she'd done it all before.

Princess Celestia returned a moment later, a tray of freshly baked pancakes being pulled along behind her with her magic. She proceeded to levitate over some bibs, fastening them around the necks of both big foals. Then she used her magic to put the pancakes onto two separate plates.

"Pancakes!" Cheerilee cheered as she raised her hooves into the air and licked her lips!

Twilight felt sorely tempted to reach out a hoof when one plate of pancakes was placed before her. The sweet smell sorely tempted her taste buds. It took all the willpower she had not to start drooling like Cheerilee was.

But Celestia pulled the plate away, as if sensing what Twilight was going to do. "Ah ah ah!" She playfully lectured. "You have to wait for Mommy to cut them up first." And that is exactly what she did: Using a fork and a knife to cut the pancakes into small, foal sized portions. They were full of syrup and warm butter that had been spread over them, which only made them seem even more irresistible.

As the padded princess waited patiently for the pancakes, she couldn't help but notice that next to Cheerilee's plate of pancakes was also a small bowl of oatmeal. That struck her as odd. Sensing that she would not get a straight answer from the earth pony mare, Twilight turned to Princess Celestia. But before she could ask a question, one of the cut up pieces of pancake was inserted into her mouth. The taste was so sweet that she forgot about everything else, and just concentrated on eating as many pieces of pancakes as were provided to her.

Cheerilee seemed to be much the same, content to let the sun princess feed her. Even so, she and Twilight both found that traces of syrup and pancake crumbs were getting all over their faces.

Princess Celestia wasn't bothered in the slightest by how messy her foals ate. She just waited until the last of the pancakes had been devoured, then levitated over a wet rag and started cleaning Twilight's face. "Those pancakes must've been really good if you made such a mess eating them." She playfully commented.

Twilight nodded back as her face was slowly cleaned. "Uh-huh. Pancakes are yummy!"

Meanwhile, Cheerilee seemed to get an idea. As she waited for her turn to have her face wiped clean, she reached out a hoof to grab her bowl of oatmeal. It had long since stopped being fresh and warm, but she didn't care. Instead of putting it into her mouth, the padded earth pony simply pulled back the seat of her diaper and poured the entire bowl's worth of oatmeal into her diaper. Then she leaned back in her chair and giggled as she squirmed about. "Heh heh, squishy!" And she pretended to gag, clearly intending for the oatmeal to be a substitute for something else.

Celestia playfully frowned when she witnessed the display. "Really, Professor Pampers? Did you have to do that now? Couldn't you have waited until we were done with breakfast?" She got up and trotted over, pretending to sniff the air. "Someone's a very stinky filly, it seems."

"Heh heh, stinky!" Cheerilee babbled and cooed as she wiggled about in her oatmeal filled diaper. Seconds later, she was levitated out of her chair as her diaper was pulled back for an inspection.

The sun princess kept up the act of treating Cheerilee's oatmeal prank as the equivalent of a messy diaper. "My goodness! You're almost as stinky as Twily! We'd better get you changed right away!" And she fanned a hoof across her nose in playful fashion.

Cheerilee, for her part, just cooed and clapped her hooves.

A small part of Twilight couldn't help but feel jealous when she watched the off-duty teacher be carried off by the sun princess. She looked down at her own diaper, noticing how pristine and clean it was. In that moment, something in her wished that she could've spilled something to make her diaper wet. Then she blinked in surprise at where that feeling had come from. "Why am I jealous?" She thought to herself. "It's all just an act, right? I'm not actually mad that Princess Celestia is treating Cheerilee as younger than me, right? She's always said I don't have to be the big filly if I don't want to be."

Unable to come up with a good answer, the padded princess just passed the time by turning her thoughts to other things: Wondering what sort of fun activities she and Cheerilee would have together after Cheerilee came back from having her "stinky" diaper changed.

Fortunately, Twilight didn't have long to wait. It hadn't even been five minutes before Princess Celestia returned, still carrying Cheerilee through the air even though the earth pony mare was now clad in a clearly spotless diaper. "Now what do you say to Twily for letting her borrow some of her diapers, Professor Pampers?" The alicorn mare with a majestic white coat asked as she set her charge down.

Cheerilee immediately looked Twilight in the eyes and in the best foalish sounding tone possible she said. "Thank you, Twily." Then she trotted over and gave her fellow padded pony a hug.

Celestia smiled and cooed with exaggerated praise. "Good job, Professor Pampers! It's always important to say thank you when somepony lets you borrow their things. And lucky for you, I always make sure to get the biggest, poofiest, most absorbent diapers possible for Twily."

Twilight blushed a bit. "I'm not that much of a stinker, am I, Mommy?"

The sun princess chuckled. "Maybe you are, just a little. But I'll love you no matter how stinky you are or how many of your stinky diapers I have to change. And I'm not just saying that because you sometimes use the potty."

"Thanks, Mommy," Twilight replied as she hugged her fellow alicorn tightly. "You're the best mommy ever! I mean it!"

"Mommy!" Cheerilee babbled as she eyed the taller alicorn mare. She seemed to be settling into her role very quickly and very easily.

Smarty Pants then questioned the alicorn mare with a majestic white coat. "So now that Twily and her playmate have had breakfast, what are we going to do next?"

"Something I think you'll agree is very fitting considering who Twily's playmate is." Celestia declared as she approached the padded mares, and teleported them away with her.

Upon returning to the bedroom that doubled as Twilight's secret nursery more or less, the padded alicorn was utterly astounded by the sight that greeted her eyes!

An entire corner of the room had been walled off by large guard rails, and the floor between the rails was covered with a soft, baby pink colored foam. Several cushions and pillows had been laid out in perfectly aligned rows, with some of them being sat upon by various stuffed animals. A small chalkboard of sorts was propped up against the wall, positioned so that it could be seen no matter how far away one sat. And just in front of the chalkboard was some kind of desk. To top it off, there were two unoccupied baby bouncers the same colors as the coats of both Twilight and Cheerilee, and they were set up right in front of the desk.

In short, it seemed that one corner of the bedroom had been turned into a classroom of some sort. The color of the baby bouncers left no doubt as to who their intended occupants could be. The only question left was who was going to be the "teacher"? It couldn't be Cheerilee. Or could it? Was Cheerilee going to give a pretend lecture about how to be a foal, and use Twilight as an example?

Princess Celestia quickly explained. "When I got Professor Pampers here," She briefly gestured to Cheerilee. "To be your next playmate, Twily, I started thinking: Since you're so smart, why not show it off? There are a lot of things you could demonstrate: You know your ABCs and how to count to ten. But then I started thinking about the things you don't know. And that got me to think that maybe you'd enjoy a day in class."

"So, Twily's going back to magic kindergarten?" Smarty Pants questioned.

At that, Twilight's pupils shrank and she gulped! "No! Not magic kindergarten!"

Celestia immediately moved to reassure the frightened alicorn. "It's not magic kindergarten, Twily. I know you don't have good memories of it. This is something more on your level: More like magic preschool."

The padded alicorn slowly came to her senses after hearing those words. "Oh thank goodness," And she pleaded. "Please don't ever make me go to magic kindergarten, Mommy! I'd rather stay with you."

The sun princess firmly vowed as she held tight to Twilight's hoof. "I promise, Twily. I'll never send you to magic kindergarten," She then calmly added. "You and Professor Pampers will be attending lessons for today."

"Yay! Preschool!" Cheerilee cheered again, before rushing over to the guard rails. But she stopped upon reaching them, rather than climb over them even though she could easily do so.

Twilight trotted over, eyeing her fellow padded pony. "What's wrong?" She asked.

Cheerilee babbled and promptly plopped down onto her poofy, padded posture. "Too high." She gestured to the guard rails, as if they were taller than they actually were.

The padded princess shook her head from side to side as she got an idea. "Nu-uh, not too high," She proceeded to try to lift the off-duty teacher from behind in order to boost her over the guard rails and into the classroom. "You can make it."

The diapered off-duty teacher, with help from Twilight, managed to clumsily straddle the guard rails. She landed on the classroom side as her diaper crinkled and compressed, cushioning the blow. From there, she scooted across the floor until she reached the bouncer with the same color as her coat. She managed to climb into it all by herself, taking great pride in her accomplishment! "Hooray!" She cheered, and started bouncing to her heart's content.

As for Twilight, she first boosted Smarty Pants over the guard rails, before climbing over them herself. She carefully levitated Smarty Pants into one of the empty seats immediately behind the baby bouncer. Then she waddled towards the baby bouncer reserved for her, and climbed into it. It felt so... surreal, even considering all the other things she had said and done as a foal. It really helped her to feel little.

Princess Celestia appeared at the desk near the chalkboard a moment later with a flick of her horn. She smiled, watching her charges bounce up and down repeatedly in their bouncers. They were clearly having the time of their lives, which is exactly what she wanted to see.

Even so, magic preschool was magic preschool. So the sun princess gently tapped a ruler against her desk, drawing the attention of all her "students". "Okay, everypony, please settle down," She spoke in her best teacher voice. "It's time for magic preschool to begin," Using her magic, she picked up a piece of chalk and wrote her name across the chalkboard. "I'm going to be your teacher: Miss Celestia. Now let me explain a few rules:" Beneath her name, she scribbled out a few numbers in chalk, then pointed to each one. "Rule number one: No disrupting the teacher while she's speaking. If you need to ask something, please raise your hoof."

Twilight and Cheerilee slowly ceased in their bouncing, eyes fixated on the alicorn with a majestic white coat.

Celestia continued, pointing to the second number. "Rule number two: Students are to remain in the classroom at all times, no exceptions. If you need to leave, you must ask a teacher to go with you," Then she pointed to the third and final number. "And finally, rule number three: Students must be on their best behavior while class is in session. Any student who disobeys will be sent to the time out corner." She gestured a hoof to a rather large stool at the opposite end of the makeshift classroom. True, there wasn't anything like a dunce cap or a paddle next to it. But the stool alone conjured up imagery intended to command obedience.

Satisfied with the lack of a response from her "students", the sun princess erased everything she had written on the chalkboard and cleared her throat. "Now then, let us begin today's lessons. We'll start with the alphabet, then numbers, and then colors," She proceeded to draw a large letter "A" on the chalkboard. "This is the letter A. It is the first letter of our alphabet, and the last letter in the word Equestria. A is for apple."

Slowly but surely, the elder alicorn guided both Twilight and Cheerilee through the alphabet letter by letter. She took the time to explain anything that might confuse her students. Then, at last, she reached the letter z, and drew a large "Z" on the chalkboard. "This is the letter Z, as in zebra. It is the last letter of our alphabet," After pausing for a moment, she proceeded to bring out some comically large alphabet blocks. "Now, here is a way to see if you all can remember what I've taught you," She levitated the blocks over to the big foals, and brought a small hourglass timer as she explained. "How many words can you make, and how many letters can you use before all the sand in this hourglass moves from the top half to the bottom half?"

Twilight felt confident in her abilities. But looking across to Cheerilee, she could see the diapered earth pony seemed more interested in stacking the blocks and building shapes with them rather than use them to spell words.

Looking back to Smarty Pants, Twilight seemed to get an idea in her head. After all, this wasn't really a contest. And it wouldn't be fair to take advantage of what she knew. If Cheerilee was having fun just the way she was, the padded princess decided she would join in.

"Are you ready?! Go!" Princess Celestia declared, and turned the timer over. Sand slowly began to pour from the top half into the bottom half. Then she stood by the chalkboard, ready to keep score.

Cheerilee quickly began arranging her blocks into a small tower, struggling to build it up at all before the uneven motion of her bouncing caused them to fall. Undeterred, she just picked them up and started building with them again, this time trying to make a small triangle with them.

As for Twilight, she was stacking blocks end to end with no rhyme or reason. She had no thought whatsoever as to what she should do with them.

The sun princess watched the infantile display from the big foals with that motherly smile of hers. "Cheerilee is learning a lot from Twilight. Or maybe it's the other way around," She thought to herself. "This is working out even better than I expected it to be. Maybe this is what Twilight's really needed, somepony on her level." Sure, there was still that lingering concern from the talk she'd had with Luna. It probably would never fully go away. But for now at least, it didn't seem to be a problem. And Luna had yet to say anything further about the state of Twilight's mental state.

At last, the final grains of sand reached the bottom of the hourglass timer. The "test" was over. Celestia took one look at the chalkboard, and found that neither Twilight or Cheerilee had managed to spell a single word with their blocks. She pretended to be disappointed as she shook her head. "Well, I guess we'll just have to come back to this lesson later." She declared and erased everything on the board again.

Cheerilee wasn't the least bit concerned about having failed the "lesson". She just kept stacking and re-stacking the blocks until they were taken away from her, at which point she occupied herself by using a free hoof to poke at her padding. She was in such a carefree state that she either didn't notice or didn't care that she was drooling again.

Twilight was only slightly better. She was silent, concentrating on using her magic to carefully position her alphabet blocks as best she could. Yet as she was in the middle of stacking them, hoping to build the biggest block tower yet, they were snatched away from her by the glow of Princess Celestia's horn.

"Alright, my little ponies," The alicorn mare with a majestic white coat declared. "That's enough for now. Playtime can wait. Now is the time for learning," Setting the blocks aside, she began drawing new symbols on the chalkboard. "Let's move on to numbers, shall we? Then we'll move on to colors, and then if there's time we'll come back to letters."

Just then, however, there came a knock at the bedroom door. It was all the way on the other side of the room, but it was still possible to hear the knock.

Princess Celestia seemed to briefly become worried if the look upon her face was any indication. But it faded just as quickly as it had appeared as she stood up and straightened her posture. "Better see what this is about," She then instructed to Twilight and Cheerilee. "Both of you stay here. I doubt you'd want anypony to see you like this. I'm sure this won't take long." She then teleported out of the classroom. After taking a moment to compose herself, she headed to the door to answer it.

Mere seconds after the sun princess had gone to the door, however, Twilight ceased in her bouncing as she felt a familiar twinge in her bladder. It was faint, but it wasn't going to stay that way for long. Her eyes drifted off into the distance, eyeing the bathroom. Just her luck that it was practically on the other end of the room, near the door. If she tried to make a break for it, she was sure to be spotted. She thought about trying to teleport to it. But then she hesitated as she remembered Princess Celestia's earlier instructions.

Cheerilee seemed to sense what the padded alicorn was thinking and feeling. For she ceased in her bouncing and leaned across to Twilight, asking her point blank. "What's wrong, Twily?"

Twilight bit her lip. "I... I have to..." She stammered as a single bead of sweat trickled down her face. The urge to go was strong. She'd never really paid it much attention before, but now it seemed intent on reminding her of its presence. "But Mommy told us we couldn't go anywhere without her. And if I try to teleport, somepony might see me. Somepony I don't want to see me in diapers."

The padded earth pony mare blinked slowly, before leaning closer and whispering to Twilight. "Well, actually, studies have shown that a diaper is more sanitary than the potty, provided the diaper is changed soon after being used. Plus, with diapers, you don't have to worry about stopping whatever you're doing. You just go when you have to go. I'm sure Mommy will understand."

Satisfied with the logic, Twilight took a deep breath and sighed. She leaned back in her bouncer, relaxed, and stopped trying to fight back. Her bladder soon relieved itself, as a steady hissing sound could be heard. Her diaper slowly but surely swelled up as a damp patch formed, growing bigger by the second. In a matter of seconds, it was all over. The damp patch slowly faded and dimmed as the diaper soaked up the accident no problem.

"There. Doesn't that feel better?" Cheerilee asked in a sympathetic tone of voice. "Your diaper handled the job no problem."

Princess Celestia reappeared in the classroom a moment later. "Alright, students," She declared in her best teacher voice. "Sorry that took so long. But I'm back, so now we can-"

But Twilight interrupted, raising a hoof. "-Mommy?"

"Yes, Twily?" Celestia asked, suspecting nothing.

The padded princess struggled to hold back the tears as she confessed. "I... had an accident. I tried not to, really, I did."

The sun princess quickly trotted over, inspecting Twilight's diaper and finding it rather soaked. She was quick to scoop Twilight into her hooves, lifting her out of the bouncer. "Oh, it's okay, Twily. If you have to go, you have to go. It's not healthy to hold it in. Come on, let's get you changed," Turning to Cheerilee, she said to the earth pony. "How about you, Professor Pampers? Do you need a change too?"

Cheerilee shook her head from side to side. "Nu-uh. I good." And she proudly presented her pristine padding to the princess. A close inspection revealed that it was indeed still spotless: No wet patches or bulges, no smelly smells.

Celestia made sure to pat the diapered earth pony mare on the forehead, showering her with exaggerated praise. "Good job, Professor Pampers! No wonder you have a PHD in diaperology! Maybe you could give Twily lessons sometimes." Then she levitated Twilight into the air, carrying her across the room to get changed.

Cheerilee watched the princesses from afar, smiling and admiring the bond they shared through their roles of mommy and daughter. It reminded her a lot of the love and affection her parents had shown her throughout her life. They had allowed her to enjoy her foalhood to the fullest extent: Weaning her off from bottles and breastfeeding, getting her out of diapers, and accomplishing all the major foalhood milestones at a reasonable age. She had been right in the middle of her peers on such issues, and even after discovering her love of teaching as a filly she had still found time for fun and games.

It was easy to see why someponies might like to return to a more carefree and innocent time. This experience was certainly giving the earth pony mare a lot to talk about when next she held a class on foals and on foalcare.

Celestia quickly changed Twilight's diaper, and then brought her back to the classroom. Much to her surprise, a hoof was raised by none other than Smarty Pants. "What is it, Smarty Pants?" She asked the doll (despite knowing who was really speaking through it).

"Could I join in the classroom too? I want to be with Twily and Professor Pampers, and go to school." Smarty Pants pleaded.

The sun princess smiled and nodded. "Of course you can join, Smarty Pants. There's always room for more. Thank you for asking the right way," She then cleared her throat, drawing the attention of her other students. "Class, we have a new student joining us," Using her magic, she brought forth the old doll and said. "This is Smarty Pants. She's here to learn just like the rest of us," Then she encouraged. "Say hello, Smarty Pants."

"Hello, everypony." Smarty Pants sheepishly greeted.

Twilight giggled and waved a hoof. "Hi, Smarty Pants! I'm glad you're here. Things are always more fun with you around."

Cheerilee also giggled, watching as Smarty Pants was placed at an empty desk to the right of Twilight's bouncer.

Princess Celestia waited for a moment, before clearing her throat again. "Now then, everypony, let's get back to today's lesson. Shall we?"

The rest of the day was a fun filled blur to Cheerilee, even to the point where she had an actual accident in which she messed herself. It had only partially been intentional to see what it felt like, and the smell alone was enough to make her regard it as something she would never do again no matter what.

When at last the day ended and Twilight went to bed for the night, Cheerilee was sad to see it all end. Even so, she was glad to get out of diapers.

Next morning, Cheerilee slept later than usual. She'd accumuliated so much earned time off that nopony, least of all the EEA, had batted an eye when the earth pony mare had decided to use some of it. She still had at least today off, which gave her a chance to reflect on everything that had happened.

Next time, perhaps she would take up Princess Celestia's request to be fully mentally regressed, instead of merely trying to act like it.

When at least Cheerilee did wake up, she was surprised to discover a letter addressed to her sitting on a desk near her bed. Being naturally quite curious, she picked it up and examined it. The letter read as follows:

Dear Cheerilee,

I probably don't need to do this, but I want to thank you again for agreeing to be Twilight's playmate. And I know I can trust you to keep this a secret from ponies who aren't in the know.

From one teacher to another, I have nothing but respect for the sense of loyalty and affection you inspire in your students. And I see a similar bond reflected between Twilight and myself since we've started these mother/daughter playtime sessions.

I know I don't need to reward you, especially not since you've still got a lot of saved days off ready for use in any emergency. Even so, I hope you'll at least consider the offer to be a guest teacher at my school someday. You strike me as an excellent pony to help teach about earth pony magic and cutie mark magic to ponies who aren't familiar with such subjects.

Sincerely,

Princess Celestia

At that, the earth pony mare felt her heart figuratively skip a beat. Being invited to teach at a prestigious school like Celestia's School for Gifted Unicorns would be a very high honor indeed.

Well, that offer would have to wait a while. Right now, Cheerilee wanted to make use of her newfound insights into foals and foalcare while the experience was still fresh in her mind. "I wonder if maybe I should lean into my Professor Pampers persona for such classes," She thought to herself. "After all, ponies always learn best through direct experience. And many of the ponies who most need a lesson in foals and foalcare are a lot older than my usual students."