"Um… Twilight? Why are we doing this again? Not that I doubt you or anything, but…" asked Fluttershy, her voice trailing off into in audible mumbling.

Twilight looked up from her notes and glanced over at her yellow friend, idly dragging her front left hoof across the library's wooden floor. She was so adorable when she was nervous. Granted, she was nervous most of the time, and she was still adorable when she wasn't.

"Well, Fluttershy, I ran into Bundle Joy yesterday evening, and it got me thinking. I have plenty of books on pregnancy and equine gestation, but all of them are from the perspective of the mother."

Fluttershy gave Twilight a funny look. "Well, of course they are, Twilight. Fathers don't get pregnant."

Twilight sighed. "Well, seapony fathers got pregnant, but that's not the point. Think about it, Fluttershy. Isn't there somepony else involved in a pregnancy?"

Fluttershy's eyes widened in comprehension and her mouth an 'O' as she put two and two together. "The foal! How could I have forgotten about the unborn foal? So that's why–" Fluttershy trailed off as Twilight abruptly started talking again.

"Exactly. Of course, this makes sense; after all, mares write textbooks and foals don't. How much can you remember from your time in utero, Fluttershy?"

Fluttershy startled slightly at the odd question. "Wh–When I was in my mom? Umm… barely anything, really. I remember hearing her heartbeat, and feeling safe, but even that's really faint and blurry."

Twilight nodded, and Fluttershy relaxed, glad that her answer had satisfied her friend. "That's more than I can remember. Any other questions?"

"Um, well, what exactly are we doing again?" Fluttershy shied back slightly, expecting to be scolded for not paying attention to, understanding, and/or remembering the bookworm's earlier explanation.

Instead, Twilight merely grinned at the opportunity to further show of her brilliance. "I am going to enter your uterus, make some observations, and record them when I come out."

"And you're sure you'll be alright?" asked Fluttershy, her first not shock at the bizarreness of the scenario, but concern for the safety of her friend.

Twilight nodded. "The spell will teleport me into the womb of the nearest mare, and hook me up just as a fetus would be. Even if something goes wrong, there's a fail safe if I'm not out in 23 minutes."

"Twenty three?"

"Well, 22 minutes, 49.2035 seconds. Anyway, are you ready?"

Fluttershy nodded, and took a wider stance to make room for a larger belly. Twilight's horn began to glow.

"Um, Twilight?"

Twilight's horn dimmed. "What, Fluttershy?"

Fluttershy squeaked. "Um, I'm really sorry for interrupting you, but why me, exactly?"

Twilight sighed. "Because of your job, lifestyle, and maternal nature, you're the least likely to be negatively affected by being… 'pregnant', with me. Is that all?"

Fluttershy nodded.

"Okay then!" Twilight turned back to her notes, double-checking her understanding and memory of the spell, and finally turned to face Fluttershy, eyes closed in concentration. "Well, here goes nothing!"

Twilight took a wider stance herself, channelling her magic through the alicorn of her horn, willing it to take the form of her choosing. This conscious control over one of the five fundamental forces of the universe, feeling it course through her and follow her command, was one of the student's favorite experiences, another being studying the elegance of magical theory, how simple concepts could give rise to such diverse and complex, yet interconnected, spells.

She could bask in the mathematical beauty of the universe later, however. Now, she had work to do, if it could be called work. As she focused on the spell, running through it in her mind's eye, strands of magic began working around her, almost like an amniotic sac, and she began to shrink along with the web of magic.

At this point, the spell was essentially self-directing, and she felt her mind going fuzzy. Then, with a flash of light, she vanished.

~=#=~

As the haze lifted from her mind, Twilight took a small amount if pride in the fact that her spell had worked. Of course, she hadn't expected it to fail, but a success is a success, and she smiled proudly.

The first thing she noticed was what she didn't notice. She had expected to hear an eep of surprise from Fluttershy, or at least feel a jump. She also hadn't felt Fluttershy thump to the floor, so she must've just been prepared.

Twilight began mentally taking notes to be copied into paper later. As expected, everything was pitch black. She could wait for her eyes to adjust to see what little light filtered in from the library, but in the meantime she would have to rely on her other senses.

Of course, the most prominent sensation was that of Fluttershy's heartbeat. It had been somewhat rapid at first, but settled over time. Listening closely, Twilight noticed that it seemed to sync up with the rhythm of her own heartbeat.

Huh, that's odd. thought Twilight. Our circulatory systems should be separate, exchanging oxygen, nutrients, and waste via diffusion in the placenta.

Twilight shifted slightly to feel around her, and something made her freeze. She felt a stirring in her own womb.

Wait, what‽ Why in Equestria would I be pregnant now?

Her mind tried to puzzle through the situation. Slowly, pushing her umbilical cord out of the way, she found her abdomen.

Sure enough, there was a significant pudge to it, as if she were 9 or 10 months pregnant. Timidly, she gave it a poke, as if she could press it flat like a whoopee cushion.

She gave a start when she felt a pressure from outside push at her.

Gears turning in her head, she gave a quick kick to the womb around her, only to feel one from inside her at the same time.

Hold on a second. Am I pregnant with… myself‽

Experimentally, Twilight concentrated, and soon her horn began to glow with a soft violet light. As her eyes readjusted themselves, she could make out the walls of the womb around her through her amniotic sac, and could see her umbilical cord twist and turn and curl, ultimately ending at her belly. Most importantly, however, she saw her suddenly rounded belly, and a faint purple glow shining from deep inside it.

Her mind began turning over, trying to puzzle out what exactly had gone wrong.

What'd do wrong‽ Oh Celestia, this could be bad. Was I distracted? No, Fluttershy had– Wait.

She went through the spell in her head, and her eyes widened in realization.

Oh. Of course. Duh. How could I have been so stupid‽

As Twilight put two and two together, everything began to make sense. Not a fan of superfluous specificity or unnecessarily uni-tasking spells, she had created the spell for a general case, and instead of creating an "enter Fluttershy" spell, she'd created an "enter the nearest mare" spell. Somehow, she had completely overlooked the fact that she was a mare, and she had certainly been closer to herself than Fluttershy.

She considered trying to teleport out, but she wasn't sure where the library was in relation to her, trapped in some kind of fractal distortion of spacetime. She decided to wait out the spell, and use the time to make observations, and more importantly, to figure out a way to comfort Fluttershy after her sudden disappearance.