Starlight's Secret

by hawthornbunny

Rating: everyone
Tags: Starlight Glimmer, Twilight Sparkle, Slice of Life, My Little Pony: Friendship is Magic, Sad, Spike
Length: 3086

Twilight finds out that Starlight Glimmer is secretly an Adult Baby.

Starlight Glimmer has a secret; a side of herself that she prefers to keep private from most other ponies.

Unfortunately for her, Twilight doesn't quite understand what "privacy" means.

This is an Adult Baby fic.

This story was inspired by Twily's Alone Time by Zubric. Thanks to abdlpony for prereading!

Published 2016-04-19 23:10:01 UTC
Last updated 2016-04-19 23:10:01 UTC

Starlight's Secret

"Come now, Radiance, do you really think you can win?" hissed the shadow drake, ceasing his barrage of flame momentarily. "You cannot escape. Your friends are defeated, and soon, you will join them."

"That remains to be seen," Radiance retorted from behind her shield of pure energy, the only thing keeping her from being roasted alive. "I've fought bigger and uglier things than you. Guess what? They lost."

"I am no ordinary creature," sneered the shadow dragon. "I am the heart of the void. I am immortal. I am -"

"What if she doesn't realize that the subchecklists are referencing items in the master checklist?" Twilight asked, her wings fluffing in sudden concern. "I'm not sure I explained that very clearly. She might start doing the tasks out of order!"

Spike pinched the bridge of his snout and closed the graphic novel, placing it beside himself on the rail station bench they were currently sitting upon. A black dragon wreathed in mist glared at up him with soulless yellow eyes, behind some large block lettering that read "BEWARE THE TERROR OF VORTEX!". The Friendship Express sat in front of them both, gleaming and hissing proudly as it took on water via a hose.

Twilight opened up her saddlebag and retrieved a furled scroll from within. "I think I should go back and go over the list breakdown again, just to make sure -"

"Twilight, she's not a baby," Spike said curtly. "Starlight's a smart mare. I'm sure she'll figure it out."

Twilight nodded, deflating slightly. "You're right. I don't know why I'm so worried."

"Nor do I," said Spike, rolling his eyes. "I mean, she's not going to take the castle for a joyride or anything."

"I know..."

"Besides, didn't you say you wanted to give her space to do what she wants and make her own decisions?"

Twilight nodded. "Yes I did. I'm sorry, Spike. I'm just sure I've forgotten something, that's all."

Spike shrugged. "If you can't remember it, it probably wasn't important." He grabbed his comic book again and returned to the battle taking place within the Cavern of Souls.

"- a real bore!" Radiance yelled. She threw up her shield again just in time for another blast of tartaral fire to slam against it. Her coat sweltered, lungs protesting at the superheated, deoxygenated air.

The shadow dragon Vortex leered at her. "Do you know what it feels like to be burned alive by dragonfire?"

Radiance groaned, her power bracelet glowing white hot from the efforts of maintaining the shield. "Is it worse than having to listen to you?"

Vortex let out an irate roar-

"Homework!" Twilight yelled, making Spike jump. The comic leapt up out of his claws. "Spike! I forgot to give Starlight back her assignment!"

"What?" Spike asked impatiently.

"Starlight completed my assignment on Friendship In The Paleo-Pony Period, but I forgot to return it to her after I marked it!"

"...so..."

Twilight hopped off the bench to her hooves, giving her wings a few quick stretches. "Spike, she worked so hard on it. She must be worrying about how she did! I know I would be. And if I don't give it back to her now, she'll have to wait another three days until we get back from Canterlot!"

"Well..." Spike flicked idly at one of his neckspines. "Why not go back to the castle and give it to her? The train's not going anywhere yet. You've got time."

Twilight looked conflicted. "I don't know, Spike... what if it leaves early?"

"Your number one assistant isn't going to let that happen," said Spike. "Besides, you're the Princess. It's not like they're going to leave you behind. Just go now while we've still got time."

Twilight smiled at her number one assistant. "Thanks, Spike. Okay, I'll be back in a minute."

Spike flicked the comic open again as Twilight burst into a cloud of pink sparkles and vanished. "Why are dragons always the bad guys, anyway?"

*POOF*

Twilight appeared in the middle of her study, and wasted no time in retrieving Starlight's completed assignment from her filing system. Starlight had achieved a solid A, which filled Twilight with a warm sense of vindication. After her failure to educate Rainbow Dash on the history of the Wonderbolts, she had realized that she'd allowed herself to become too complacent. Overconfident, even. She'd firmly believed that between her vast knowledge and her tried-and-tested studying techniques, that her teaching methods would be foolproof... and then Rainbow Dash had blown all her efforts to smithereens.

Not that Dash was a fool, of course. She knew that Rainbow was as smart as anypony else. She just hadn't understood before then that there were different kinds of smartness. It had been quite a blow to her pride, but she knew now that she was a better teacher for having had that experience.

Fortunately, Starlight seemed to be much more of a kindred spirit when it came to learning. She devoured books with frightening efficiency, and had superb recall - perhaps a little too superb, Twilight mused, for she had noticed that Starlight occasionally gave correct answers without properly understanding the logic behind them.

She flicked through the neat stack of folios - Starlight had written a lot on the assigned subject - and made sure it was all there and accounted for, before vanishing again -

*POOF*

and reappearing in Starlight's room.

"Sorry this is so late!" Twilight said, realigning the papers and presenting them to her student. "I completely forgot about returning this to you... before..." Her voice trailed off as her eyes properly took in Starlight, who gazed back in wide-eyed shock.

Starlight's mouth was hidden behind the wide mouthguard of a large, daffodil-yellow pacifier. Her manestyle was different; instead of her modest coiffure, her mane was bunched up into two squat pigtails, secured with tight ribbons, the remainder sitting comfortably in loose, bushy bangs which drooped almost to eye level.

But the most noticeable, and least explicable new feature of Starlight's appearance, was a cream-colored diaper that wrapped and hugged her hindquarters, reaching almost midway along her barrel. A repeating pattern of blue crescent moons and yellow five-pointed stars was dimly printed over the surface, and colorful tapes held it together snugly, ensuring a tight, secure fit.

Starlight's horn shimmered with mint-green magic, removing the pacifier from her mouth. "Twilight," she said dully.

"Er... hello, Starlight," said Twilight. She knew that she'd just been saying something, but all of a sudden, she'd forgotten what it was.

"You're back from Canterlot," Starlight noted. She stood stiffly. Her hooves hadn't twitched a muscle since Twilight had appeared.

"I, er... no, we haven't left yet," said Twilight. Her throat began to tickle, and she gave a little cough. "I... just came to return your assignment. You did really well."

Starlight's eyes followed the stack of papers as they slowly trundled toward her in Twilight's purple aura, coming to a halt beside the floating pacifier. She stared at them, but didn't move to take them.

For quite a number of moments, neither of them said anything.

"Well then," said Starlight.

"I..." Twilight coughed again. "I'm sorry. I should have knocked. Or, you know, used the door. Eheh."

"It's okay," said Starlight. Her expression didn't seem to back that up, though. Twilight felt pretty sure that Starlight was far from okay about this; possibly, the furthest from okay that it was possible to be.

"No, it's... I really am sorry, Starlight."

"You don't have to be sorry," said Starlight, her ears turning redder and redder. Twilight heard a soft scrunch from Starlight's rump as the unicorn took a deep breath in. The diaper, she noted, made a significant difference to Starlight's figure; Twilight wondered if Starlight was even able to walk right now. "This is just... it's just... something that I do, okay?"

Twilight nodded. "Yes. I understand."

The levitating items twinkled through another bout of silence, during which Twilight was able to place the distinctively sweet, chalky smell in the air as being talcum powder.

"I, er... anyway, I marked your assignment. I was very pleased with your friendship matrix," said Twilight. "You got an A."

"That's great," said Starlight. She reached out with a hoof to take the assignment back, but Twilight seemed to have forgotten she was still holding it; it took a few tugs before the Princess released it from her telekinetic grip. Starlight yelped and tottered backward, landing on her well-padded rump.

"Oh! Sorry," Twilight squeaked, as Starlight brushed her bangs out of her eyes and tried to get back up on all fours. Her hindlegs scrabbled furiously on the exquisite crystal floor, but with all the padding between them, her hooves couldn't purchase properly, and just slipped and slid every time she put any weight on them.

Her face wrinkled into an angry grimace as Twilight hesitantly offered a foreleg to her. Blushing a fierce shade of ruby, she took it and hauled herself back to her hooves. She took in a breath to calm herself, but found that it came in rather shakily. The bottom of her throat began to tighten.

Oh, Celestia, no. Please... not now. Not that. Please...

"You should go," Starlight breathed. "Don't want to keep Princess Celestia waiting." She turned away, pressing her suddenly-raw eyes against her forehoof.

"The train's not due to leave yet," said Twilight.

Starlight's nose gave a tiny, wet snort. "Please go," she said quietly, screwing her eyes shut tight.

Twilight looked at her in alarm. "Starlight..."

"Go!" Starlight yelled, her voice cracking. She stamped her hoof hard on the crystal floor, hard enough to hurt, anything to stop the flood that she knew was coming. "Just go to Canterlot! Go! Please..."

A pair of warm purple forelegs and wings encircled her, and she knew it was pointless. She managed to muffle her wail into Twilight's chest, tears soaking the Princess of Friendship's fur as the alicorn's body tightened round her. Her pigtails bobbed and undulated with every sob.

"Wh-Why can't I just win for once?" she blubbered. "All I ever wanted was to be happy. Is that s-s-so bad? Wh-Why can't I have that?"

"Starlight, please don't cry. It's going to be okay," Twilight said gently.

"Y-You would say that! Everything always works out for you," Starlight moaned.

"Starlight, please listen to me. Whatever's going on here... it's okay. You haven't done anything wrong, and I'm not mad. Okay?" When Starlight didn't respond, she gently stroked the back of Starlight's mane, which only elicited strangled sniffles from her.

"I b-bet you're loving this, aren't you," Starlight mumbled. "Th-The great Starlight Glimmer, reduced to a s-silly little sobbing filly. Another foe conquered by the P-Princess of Friendship..."

"It's not like that at all, Starlight," said Twilight. "I hate seeing my friends upset. No matter what this is about, I want to help you."

Starlight sniffed wetly. "I didn't want you to know about this."

"I understand that," said Twilight. "But I can't change what's happened." She elected not to raise the option of time travel in this instance. Starlight merely nodded, continuing to look miserable. Twilight continued to hold her, gently rubbing the beleaguered unicorn until her breathing calmed down some more.

"Y-You really should go," said Starlight, sliding a hoof under her bangs and wiping away some tears messily. "Important royal duties."

"Friendship is my royal duty," said Twilight earnestly. "Princess Celestia will understand that."

Starlight snorted. "I... I suppose you must think this is pretty stupid, right?"

Twilight gave a shrug. "I never judge," she said, regarding the oversized diaper that Starlight's rump was currently swaddled in. "Starlight, are you a... are you an adult foal?"

Starlight's ears perked, and she peeked up, her reddened eyes meeting Twilight's curious gaze. "You know what that is?"

Twilight pursed her lips thoughtfully. "I don't know much about it. I've only heard the term used here and there. I know that there are ponies who enjoy the idea of reliving their foalhoods. Come to think of it, I'm not sure Pinkie Pie's actually stopped living hers yet."

Starlight gave a giggle, managing a weak smile. "Pinkie Pie isn't an AF."

"But you are."

Starlight sighed and nodded. "Yes."

Twilight nodded, gently swaying Starlight. It seemed to calm her down a bit more.

"It's just... it's kind of... ugh, it's hard to explain. It's just something I've liked doing, ever since... well, ever since I grew up, I guess."

Twilight nodded again, raising a brow as she thought about this for a moment. "So... when my friends and I were being held captive in the village... were you...?"

"Huh?" Starlight blinked, unsure what Twilight was getting at. "Was I doing this? Oh, no, no, no. I never did it in Our Town. I couldn't. Too inconvenient." She hmmed, a pensive frown on her face. "Although now that I think about it, maybe I should have just made everypony there wear diapers. I'm sure I could have convinced them to."

Twilight gave her a stern glare. "Starlight..."

"Oh, but, um, that would have been wrong," Starlight added hurriedly. "No, I went without it for the longest time. It's only since I moved here with you that I've been feeling more... foalish," she admitted. "I think it was when we went to the Crystal Empire, and I saw Princess Cadance's little baby... I... it all came back to me. All these feelings."

"I see," said Twilight. "At least, I think I see."

Starlight pouted again. "I know you think it's stupid."

"I didn't say that," said Twilight.

"But you're thinking it."

Twilight sighed and shook her head. "Starlight... let me show you something. Maybe it'll put your mind at ease." She helped Starlight to her hooves again, and trotted out of the room. Starlight carefully waddled behind her, her face still heated. She was hardly able to believe that she was diapered up in the presence of her mentor (not to mention a royal alicorn), but it seemed like there wasn't really an out at this point.

"Where are we going?" Starlight asked.

"Just here," Twilight said after a short trot, stopping at a room at the end of the corridor and opening the door. Starlight followed her in curiously. When she saw what kind of room she was in, she blinked in surprise.

It was a little colt's bedroom. The bed was stallion-sized, certainly, but the bright, cartoony blankets weren't fit for any adult, and the toychest and Smash Fortune posters stuck on the walls sealed it. But the room made no sense to Starlight. Nopony had ever lived in this castle besides herself, Twilight, and Spike. She was sure of that. And this wasn't Spike's room.

"Why is the wall all cracked?" Starlight asked.

"Pinkie," Twilight explained.

"Oh," said Starlight. "Where are we?"

"This is a guest room," said Twilight. "I made it up for my brother, Shining Armor, when he stayed here a few moons ago."

"You did this?" said Starlight, amazed. The attention to detail was meticulous - no surprise, of course, given whose hoofiwork this was, but the room was near indistinguishable from any colt's bedroom, right down to the rumpled imaginary-town floor rug and the overflow of building blocks from the toychest. Starlight was half-convinced that Twilight had purposely arranged that mess. "Why? Your brother is older than -" Her eyes widened as the realization came to her. "Wait. Are you saying your brother is a... you know?"

"I don't know if he is," said Twilight. "But I have often suspected. He's always been a bit of a goofball, but I always thought there was more to it than that." She smiled, remembering her brother's reaction the first time he had been here. "The way his eyes lit up when he saw this room. For just a few moments, it was like he really was a kid again."

"The Prince of the Crystal Empire?" Starlight pressed, just to be absolutely sure. "He's an adult foal?"

"Well, technically, the Prince Consort," said Twilight. "And like I said, I don't know for sure."

Starlight giggled. "I can't believe it!"

"I'll ask that you don't tell anypony, though," Twilight requested politely.

Starlight snorted. "Of course I won't! In fact, you shouldn't even have outed him!"

"I just wanted to try to make you feel better," said Twilight.

Starlight gave a smile. "I do. I do feel better. I... thank you, Twilight. For this. I'm glad you're not weirded out."

"I can't deny that it's a little strange to me," said Twilight. "But that's not important. What you do is your choice. And you know... I don't know if this helps you or not... but you do actually look rather cute." she said, smiling.

Starlight's cheeks flared red again, her lips curling into an embarrassed grin. "You... you think so?" She winced and ducked her head, unable to meet Twilight's gaze. "I... you know, it's strange, but I guess I am kind of glad this happened. For the longest time, I thought you already knew and just weren't telling me. I thought Spike had told you, or he'd let it slip accidentally. Guess I don't need to worry about that any more."

"Spike?" Twilight raised a brow. "Does he know?"

Starlight nodded. "He figured it out. He's actually been helping me get hold of, uh, these..." she wiggled her padded rump meaningfully.

"Oh!" Twilight suddenly exclaimed. "Spike! He's still waiting for me! I should -"

"You should go," said Starlight softly. "I'm okay now. Thank you."

Twilight smiled. "Any time." She charged her horn for a teleport, but before she could complete it, Starlight had waddled to her and given her a grateful hug and a nuzzle.

"Thank you. For understanding," said Starlight. Twilight felt the touch of crumpled padding on her leg briefly, and wondered where Spike even knew to obtain mare-sized diapers of this kind from. Returning the nuzzle, she gave Starlight a tender peck on the forehead, before completing her teleport and vanishing, leaving Starlight on her own.

Starlight blinked. The kiss had been unexpected. That was a very motherly thing for Twilight to do. Maybe she'd just been caught up in the moment. She sighed happily, looking around the bedroom. It gave her a warm, welcoming feeling to know this was here, even if she was very much an adult filly rather than a colt.

Maybe there's a place for a filly's room in this castle, too.