Shining snorted in annoyance as he was roused from his sleep. Why is it that whenever you're trying to get up is when the bed was its most comfortable? he wondered. The knock on their door – the same noise that had awoken him in the first place – came again. Whoever it was, it became apparent that they weren't just going to give up and go away. He blindly poked at Cadance, “Sweetie, could you get that?” The only response he got was a loud snore. For a moment he considered testing to see if she really was asleep – it wouldn't be the first time she has faked being asleep so she wouldn't have to be the one to get up. After another knock, he sat up, let out a big yawn, and hopped off the bed; only now cracking open his eyes and letting them adjust to the light. This better be something good.

Their living quarters was divided into two rooms: a bedroom and a living room. On his way out of the bedroom, he passed their dresser. On top of it sat a red, stuffed seapony. A bit of stitching on its back had already split, Shining figured that it was poorly made. He had been meaning get one of the maids to fix it up, but kept putting it off. In fact, this was his first day off in a few weeks. Thankfully he didn't have many duties as the prince of the Crystal Empire – Cadance was the one to do the governing – but he still had his role as the head of Equestria's Royal Guard.

He stood, staring at the door that lead out of his living room, and considered turning around and going back to bed. A clock hung from the wall next to the door displaying the time of ten am. As the morning fog in his mind started to clear, he remembered the letter he got the other day. Oh, right. She was coming over today for a visit. Another knock came. With a groan, he opened the door and his sister was waiting on the other side. “Hm... Hey Twiley,” he said, punctuating it with another yawn.

“Wah!” Her wings shot up in surprise, and she backed up until the hallway wall stopped her. “S-Shining?”

“Yeah?” He tilted his head.

“Oh, um, I can come back later if this is a, um, bad time.”

“No, it's a fine time. Twiley, are you ok?”

Her jaw dropped at that question. “Am I ok?” She pointed at him. “Y-you... you! Are you ok?”

“What?” He felt his face to see if he could figure out what she was going on about. His snout was shorter and rounder, as was his horn. Shining checked the back of his head, taking notice of his – or rather her – mane's length.

She noticed the bedroom door behind her moving and Cadance popped her head out. “Who is it ho-o-oh! Um, hey Twilight.” She looked back and forth at the two, then pointed to Aegis. “It was all her idea,” she quickly said before vanishing back into the room and closing the door.

Aegis looked back to Twilight, who seemed even more confused now. She groaned and facehooved. “Luna fuck me with the moon...”

Aegis walked her little sister to the guest room, explaining why she was a mare on occasion, and most importantly that it was in fact Cadance's idea, not hers. Though she did spare Twilight of the more intimate details. She had no desire to share those with her little sister, and she was sure that Twilight would be thankful to know as little about that side as possible.

“Alright, here you go.” She opened the door and led Twilight into the guest room. It was pretty much the same as Aegis' and Cadance's living quarters, though smaller. The living room for it had the standard setup of a couch and coffee table in the middle with a desk off to the side.

Before she had the chance to continue saying anything, Twilight snatched out a tape measure from her bag and started taking Aegis' measurements – taking notes as well, of course. “This is quite the experiment and a very good question to ask. 'Does changing the gender of the ponies in an established relationship change how the relationship functions.' Surely there will be some changes, whether they be subtle or pronounced.”

“Twiley!” Aegis called out when she felt the tape measure measuring her underside.

“Alright, done with the measurements. Now then, what are the personality changes that you've noticed?”

“Wow, I didn't expect you to take it like this.”

“Oh, I was plenty shocked when I first saw you, but the more I think about this, the more it seems like a great thing to observe.”

Aegis simply rolled her eyes. She probably should have expected this from Twilight. All things considered, Twilight always did want to know the how and why to everything she saw. Give her something unusual and Twilight will spend days trying to figure out everything about it. Seeing her older brother being her older sister was apparently no exception.

“You didn't answer my question though, did you notice any changes in the way you behave? I have noted that your movements are different, more inline with what a normal mare's would be, was that something that happened naturally? How about Cadance – er, what is her-his name as a stallion?” As she continued her questions, Twilight came close and started poking at different spots on Aegis.

“It's Eros, and would you stop that?”

“Eros you say? That's rather fitting to be named after an ancient god of emotion. What about you? Are you still using Shining Armor or did you also pick out a new name?”

“Aegis.”

“I get it, after your special talent. Before I continue, I need to check out the palace's library.”

Aegis blinked a couple times. “For what?”

“I know there's books about common activities for sisters to do together. Oh, this is going to be perfect.” Twilight happily trotted past Aegis and out of the room.

“What just happened?”

“You can't be serious.”

“It's in the book.”

“What kind of book did you get?”

“How to Bond with Your Sister.”

“That's an actual book?”

“It would seem so.”

A kettle of freshly made tea was on the middle of the table with a couple plates of various types of strudels around it.

Twilight lifted the kettle. “More tea Princess Aegis?”

“I feel ridiculous.”

“Oh come on, don't think of it like a tea party. It's just two sisters talking over some snacks and tea. Nothing immature about that.”

Aegis sighed. “Alright, fine. It does at least sound better that way. I'll take a cup with three sugar cubes.”

“Hm, interesting. You only took one cube with your tea as Shining.” Twilight mixed in the sugar and levitated the filled cup over to Aegis.

“I have more of a sweet tooth when I'm Aegis.” She blew on it and took a sip. “Ok, this is actually pretty good.”

“You never answered my question, you know.”

“Oh, about the differences? Honestly, I haven't noticed that many. There's the sweet tooth thing, I blush a lot easier, and my ears are a lot more sensitive.”

“Are you attracted to stallions?”

Aegis stopped in mid drank and began coughing. “T-Twiley!?”

“Just be honest.”

Aegis looked away and took another drink of the tea. As if to show that she was right about the differences, Aegis gained a crimson hue to her cheeks. “Maybe a little. At least I do for Eros. When it comes to other stallions, I don't know. Haven't really thought about it.”

“You know, one pony just isn't enough of a sample size.” She scratched her chin. Now, Aegis was a bit worried. She had seen that look from her sister before and it usually led to trouble. “Perhaps with the right incentive I could get a group of volunteers to form a proper experiment. I'll need to keep tabs on them and their relationships. I'll call it 'The Effects of Gender Changes on Interpersonal Relationships.' That may be too wordy though, but at least it is direct.”

“Twiley?”

Twilight seemed to snap back to reality and looked at her big sister. “Yes?”

“What did mom say about experimenting on ponies?”

“Oh come on, I've apologized for that. Besides, they'll be volunteers this time.” Twilight took a large bite of a strudel. “Oh, the blueberry ones are great.” She snapped off a piece and levitated it over to Aegis.

“Just don't mess with their fur color.”

“It wasn't that bad.”

Aegis stared at her little sister in a deadpan expression. “You gave me black fur and a dark red mane.”

“The spell wore off, so it wasn't that bad.”

“It took a week to get my colors back to normal.”

“I thought it would look nice.”

“Really?”

“I was young and hadn't met Rarity to know about proper color combinations and contrast.”

Aegis rolled her eyes and huffed. “I had to put off asking out Cadance for the first time because of that...” She grabbed the strudel piece and ate it. “The blueberry ones are pretty good.” After swallowing and getting some more tea, “So, what do you think?”

“Think about what? Having a big sister?”

“No, about why I act a bit different this way. Is there an actual reason?”

“The why for the changes is a pretty good question.” Twilight held out a hoof. “On the one hoof there's the idea that you are just playing a role and Aegis is a character that your mind made up. Basically, she's what you think mares are like, and since you're playing a mare, your mind adapts to the role and you take on those characteristics. It really is just an act, though one so good, you don't realize it while doing it. Do you have any cliché things that you've enjoyed as a mare?”

“Well, um...” Aegis nervously scratched at the back of her head. “I have really enjoyed spending time at the spa to relax as Aegis. And, um, I like getting my hooves painted.”

“Oh? What color?”

“Light-blue. It matches my eyes.” Twilight snerked. “Hey, no laughing. I like the way it looks, alright?”

Twilight nodded. “Sorry, sorry. It just feels so weird to hear you say that.”

“Believe me, it felt weird saying that I liked it the first time.”

“Ahem, anyways, yes that could potentially be an example of simply acting the role.”

“Potentially?”

“Correct.” Twilight extended her other front hoof, not before lowering the first one though. “There's also the fact that hormones do play a major and, at times, subtle role in how we behave. So, with having an entirely new brain chemistry, some of the changes would be true personality alterations. There's the chance that some things, like the sweet tooth or the blushing could be beyond just playing a role. These traits may be impossible for Shining to possess.”

“Ok, I think I get it, but how do I know which changes are real ones and which are just me playing a mare?”

“Honestly? I haven't the slightest idea,” she said with a shrug of her shoulders. “I might be able to come up with a system for categorizing the probability of which changes are real and which aren't to a degree if I got to experiment on a large group of ponies. That would be the only way. In the mean time, it might be best to just not think too hard on it and go with what feels natural.”

Aegis nodded. “That's pretty much what I've been doing.” The two continued to make idle chit chat as they went through the rest of the tea and the snacks. “So, what's next in that book? Playing with dollies or something?”

Twilight cracked it open, and a smile formed on her face. “Nope. It's makeovers!”

“Oh... joy.”

“Would you hold still,” said Aegis as she finished putting a pair of fake eyelashes on Twilight.

Cadance had lent them a makeup case – a rather large one at that – to use. She had seemed rather amused by the idea of Aegis giving any kind of makeover or using makeup at all. As the two left the room, Aegis overheard Cadance whispering to Twilight, “If she messes up really badly, we can have it fixed at the spa later.” The case now sat in the center of the guest room's table.

I'll show her, thought Aegis. “Close your eyes Twiley.” She applied some bright pink eyeshadow to Twilight.

“What color are you using?”

“You'll see in a second.” Aegis held up the blush brush and liberally applied it to Twilight's cheeks. “I think I'm getting the hang of this.” Next came the lipstick, she made sure not to skimp on that. “We aren't doing outfits too are we?”

“No.”

“Good.” Aegis did the finishing touches, mainly making sure that the lipstick wasn't too sloppy. “Ok, now look.” She grabbed a compact mirror from the case and held it up for Twilight to see.

Twilight stared in silence at her reflection. Slowly turning her head to the left, and then to the right. She opened her mouth for a moment, but quickly closed it again.

“Well, what do you think?” Thinking on it for a moment, Aegis added, “And be honest.”

Twilight took one more look at herself in the mirror before answering, “Well, if you want me to be completely honest... I look like I belong in a circus, scaring little children.”

Aegis's ears drooped. “Heh. That bad huh?”

“In a way, I'm actually kind of relieved.”

Aegis cocked in her in confusion. “Say what now?”

“Well, it would have been kind of insulting if changing genders gave you the ability to apply makeup well.”

“You got a point.”

Thankfully for both of them Cadance had also given them plenty of wipes to clean up the results. It took quite a few of them, and a lot of hard rubbing, but Twilight eventually managed to remove all traces of her clown makeover.

“Aha!” Aegis exclaimed and pointed at Twilight, “It didn't take a professional to fix it!” Twilight stared back at her, blinking a few time in amazement, before starting to giggle. It grew louder into a full laugh, which Aegis joined in on. They leaned against each other as the laughter slowed to a stop. Looking through the case again, Aegis spotted a some nail polish containers.

After picking out a shade of red, labeled fuchsia, she held out a hoof to Twilight. “Let me see your hoof.”

“Um...” Twilight's sight went from Aegis, to the bottle, and then back to Aegis.

“Trust me. This is one thing that I do know how to do.” She motioned for Twilight's hoof again.

“If you say so...”

Going through the instructions she had gotten from Bonna Fide, and trying to mimic the way the girls at the spa did it, Aegis applied the polish to her sister's hoof. To her surprise – and likely to Twilight's as well – Aegis applied the polish perfectly without dripping any of it onto the couch or getting any on Twilight's fur.

“Color me impressed. Where did you learn how to do this?”

“Some friends at the spa showed me.” Twilight leaned back on the couch and held up her other front hoof for Aegis, who took the hint and did the same for it. “Unless you want to want to give me a makeover, I guess that's it for the makeover.”

“I don't think you left behind enough makeup during your attempt for me to even try.”

“Oh hardy har.”

Twilight focused on her hooves and Aegis could practically see the polish drying. Twilight touched her hooves to check if it worked, and then sat back down normally. “On to the next chapter.”

“If it says anything about shopping together, I'm out.”

Twilight looked through the book. “Nope, not shopping. Actually, we should skip this one.”

“Twiley suggesting that we skip something on a list? I am shocked!” Aegis said in faux surprise.

“Well...” Twilight closed the book, and Aegis saw a slight blush on Twilight's cheeks. “It's talking about boys.”

Aegis rolled her eyes. “Dear Celestia how cliché can a book get.”

“Yeah, it is amazing. So, let's just forget the book then.”

“Wait,” Aegis said, giving Twilight a curious glance. “You seemed fine with everything until this. I have a reason to not find this one interesting, but why are you trying to avoid it?”

“Reason? Who said I have a reason? So, um, let's go do anything else besides this.”

“Twiley?” Aegis poked at her sister's shoulder. “Do you like somepony?”

“M-maybe,” she mumbled, staring down at the floor. “Not that it really matters?”

“Oh?” asked Aegis. “Why wouldn't it?”

“I don't think I really have a shot with him.”

“Why don't you start by telling me a little about this guy.”

“Alright... He's an earth pony and –“

“An earth pony? Really?”

“Ugh. First Rarity and now you. Why is it so surprising that I would like an earth pony?”

“I just always figured you would want somepony that could use magic.”

“I happen to be fine dating a pony that doesn't use magic, thank you very much.” There was a certain level of aggravation to her voice, obviously upset that both Aegis and Rarity would find that so odd.

Aegis waved off her sister's indignation. “Fine, sorry. You can continue.”

“Ahem, he's an earth pony and he's the big brother of my friend Applejack. He's a large, kinda quiet, really down to earth guy... Oh, and he's a farmer.” She had a soft smile on her face while describing him. “And he is pretty handsome too.”

“Oh?” Aegis playfully nudged her sister. “You planning on telling me his name or just keep describing him?”

“Um, right...” Twilight blushed, and coughed into her hoof. “His name is Big Macintosh, though most ponies just call him Big Mac.”

Aegis nodded. “So, what did he do to get your attention?”

“Well, remember that time I accidentally, nearly destroyed Ponyville with that, Want It Need It, spell?”

“Yes, I was briefed on what happened.”

“Then you know that I lost Smarty Pants because of it. Turns out it got beaten up in all the commotion and Big Mac ended up being the last pony with it. About a month later, he brought it back to me, completely stitched up and looking good as new. A lot of guys wouldn't have done that.”

“Sounds like a nice guy.”

“He is. But...” Her ears drooped down. “It's not like I actually have a chance.”

Aegis put her foreleg around Twilight, pulling her into a hug. “Why not?”

“Because nearly every single mare in Ponyville has been trying to get his attention it seems. I can't compete with all of them.”

“It's not a competition. Listen, if this guy really is the down to earth guy you think he is, he would prefer a date invite over a mare trying to get his attention. All it takes is walking up to him and saying, 'Hey, I think you're a cool guy. Want to go on a date?' That's it.”

“I-I,” Twilight stammered. “I couldn't just walk up to him and ask him out.”

“Why not?”

“Because... because he might say no.”

“And?” asked Aegis, in a very matter of fact way. “So what if he says no?”

Twilight leaned into Aegis' hug, resting her head against her older sister's shoulder. “Right now, I think I don't have a chance. If I do that, then I would know that I didn't have a chance.”

“And what happens if he says yes?”

“I'll probably stand there dumfounded and act like an idiot.”

“Look, I know asking somepony out is tough. Heck, I asked out a freaking princess. Believe me, I'm still impressed that I managed to pull that one off. But you have to pony up and do it. Either way, you'll be able to move on. And if he does say no, you can come back to the palace. We'll eat ice cream and talk about it or something. Whatever it is that mares are supposed to do together when one is having boy trouble.”

“Really?”

“Yeah. So, are you going to do it?”

Twilight was silent for a moment before finally answering, “Yes. I'll do it.”

“Atta girl. So, what's next?” Aegis picked up the book with her magic and looked through it. “Twiley, why didn't you tell me these suggestions had age ranges next to them?”

“Because I didn't want to miss the chance to see you at a tea party.” Twilight, in a mature fashion befitting of a princess, stuck her tongue out at Aegis.

Aegis grumbled as she flipped through the book until getting to the next main suggestion, “The older sister reading a story to her younger sister.”

“Well, that's not much of a sister thing. You used to do that for me all the time.”

“Speaking of which,” Aegis pulled away from Twilight, jumped down off the couch, and walked towards the door. She looked back to Twilight, “The library here might have your old favorite.”

Twilight's ears perked her ears up. “Really?”

“I'm about to find out.”

Sure enough, the Crystal Palace Library did have a copy of it. The sisters were laying together on the couch, just like they did when they were younger – aside from the one major difference anyways. Aegis was pressed against the back of the couch with Twilight curled up into a ball on the other side of her. She held the book in front of her as she finished reading it out loud, “That's when the third pig yelled, 'And your granny can sit on a pin!'”

Twilight giggled. “I love that part.”

“Yeah, it is a pretty good line,” said Aegis before continuing to read, “Now I'm a pretty calm fellow. But when somebody talks about my granny like that, I can go a little crazy. When the cops came, of course I was trying to break the pig's door down. And the whole time I was huffing and puffing and sneezing and making a real scene. The rest, as they say, is history. The news reporters found about about the two pigs I had for dinner. They figured a sick guy going to borrow a cup of sugar didn't sound very exciting. So, they jazzed the story up with all that, 'Huff and puff and blow your house down.' And they made me the big bad wolf. That's the real story. I was framed.”

Twilight, from memory, recited the final line, “But maybe you could loan me a cup of sugar?”

Aegis closed it and laid it on the table. They continued laying there, not really knowing what to say or if they should say anything at all. Eventually, Twilight broke the silence.

“Hey sis?”

“Yeah?”

“Thanks for what you said earlier. I really will ask him out. Heh, this is one thing that's definitely different.”

“What's that?”

“I'm not sure I could have talked about that with you before. I know you're still the same pony but...” Twilight thought on what to say next for a moment, or so Aegis assumed. “But it's easier to talk to my big sister about a guy than what it would have been talking to my big brother about a guy. I hope that makes sense.”

“No, I understand. And if you need to talk more about him at some point, just say so and I'll turn into Aegis, um, me... er, you know what I mean.”

“Thanks.”

The comfortable silence came back as they just enjoyed each others presence. However, unlike the last silent moment, Aegis swore she could hear something coming from behind the couch. It was a pretty soft noise and sounded almost like a quill... writing on... paper. Aegis groaned. “Twiley, have you been secretly taking notes?”

“...yes. For science.”

Author's Notes:

BTW, the book Aegis is reading to Twilight is a real book. It's called: The True Story of the Three Little Pigs. Definitely worth checking out.