//------------------------------//
// Seperation Anxiety 
// Story: The Terrifying Tale of Two-Headed Twilight 
// by Inspector Brown 
//------------------------------//

	“Okay, Spike,” said Rainbow Dash.  “I got everypony here to the castle.  Now tell me what’s going on!”
“It’s Twilight,” Spike said, his voice catching in his throat.  “Something…strange has happened to her!”
“Yeah, we know,” said Applejack.  “Rainbow told us that already.”
“What we’d like to know is what exactly happened to her,” said Pinkie Pie.
“Is she hurt?” Fluttershy asked.  “Is she sick?”  She gasped.  “Is she dying?”
“I don’t know,” said Spike.  “I really can’t explain it.  You kind of have to see it for yourself.”
Spike took off through the front door, down the hallway toward the library.  The five ponies he had summoned followed him.  They came to a stop in front of the library door.
“Brace yourselves, everypony,” Spike said.  “What you are about to see will shock you.”
He opened the door, and everyone looked inside.  They saw Twilight Sparkle, in profile, levitating a book in front of her face.
“She’s got her nose in a book, darling,” Rarity said.  “That’s not that unusual for her, you should know that by now.”
“Not that!” Spike said.  He ran into the room, swatted the book away from Twilight’s face, and turned her so she faced the door.  “I meant this!”
“Whoa!” said Rainbow.
“What in tarnation?” said Applejack.
“Oh my goodness gracious!” fretted Fluttershy.
Rarity gasped, and fainted.
“Freaky-deaky!” said Pinkie Pie.
At first glance, it appeared as if Twilight’s head were split in half right down the middle.  However, in between the two halves, where one would expect to see the inside of her skull, there was only purple fur, so it would be more accurate to say that Twilight now had two heads.  Each head had a complete muzzle, with two nostrils and a mouth, but only one eye and one ear, on the side opposite the other head.  Her horn was intact, and appeared only on the head on the left.  This head smiled with relief when she caught sight of her friends in the doorway.  But the right head looked at them quizzically.
“Spike,” said the right head, “I thought I told you to find my friends.  Who the hay are these ponies?”
“Twilight, these are your friends,” Spike said.  “Don’t you recognize them?”
“No, I’ve never seen these ponies before,” said the right head, even as the left head nodded vigorously.
“Yes, you have,” Applejack said.  She walked into the library to place herself muzzle to muzzle with Twilight’s right head.  “It’s me, Applejack.  You know me!”
“I know Applejack,” said the right head.  “But there’s no telling if you are she.”  While she said this, Twilight’s left front hoof wrapped around Applejack’s neck, and tugged her toward the left head.  Left Head nuzzled Applejack’s neck affectionately.
Right Head turned and glowered at this.  “Don’t you even try to pretend you know this pony, impostor!” she said.  “I know my friends, and they will prove to you that I am the real Twilight Sparkle.  That is, if they ever get here.”
Left Head pulled away from Applejack, and used her horn to spell out a message in mid-air: HELP ME AJ!
“Okay, this is getting creepy,” said Applejack.  She stepped back from Twilight.
“Let me try, AJ,” said Rainbow Dash.  She flew into the room, and made eye contact with Right Head.  “So, you say you know your friends, huh?  Is one of your friends named Rainbow Dash?”
“Absolutely,” said Right Head.  “She’s one of the most talented flyers in Equestrian history.  She was recently inducted into the Wonderbolts, if I’m not mistaken.”
“You’re not,” said Rainbow.  “Now, describe what Rainbow Dash looks like.”
“Huh?”
“Come on, you’re friends with Rainbow, you must know what she looks like, right?”
“Uh, yeah, I guess so,” Right Head’s lone eye shifted back and forth.
“Then describe what Rainbow Dash looks like.”  Rainbow narrowed her eyes at Right Head.
“I…um…well…you see…uh,” Right Head stammered.  “Oh, it’s this impostor’s fault!  She stole my memories like she stole my magic!  And now she’s using that against me to trick you!”
Left Head jabbed Right Head with her horn to draw her attention.  Then, she used her magic to spell out YOU STOLE MY VOICE in the air.
“Hmm,” Rainbow said.  “I’m not sure, but I have a hunch the Twilight who can’t speak is the real Twilight.”  She turned and made eye contact with Left Head.  “Do you know who I am?”
Left Head nodded.
“How about her?” Rainbow asked, pointing at Fluttershy.  “Do you know her name?”
Left Head spelled out FLUTTERSHY with her magic.
“Good, very good,” said Rainbow.  “Now, what were the names of the feuding families you and Fluttershy met in the Smoky Mountains?”
Left Head’s eye scrunched up in confusion.  Her left front hoof, apparently under her control, tapped Left Head lightly on the brow.  She gnashed her teeth in frustration, and tears started welling in her eye.  Then, with a defeated sigh, she hung her head low, and spelled I DON’T KNOW with her magic.
“Aha!” said Right Head triumphantly.  “I remember when the Map summoned Fluttershy and myself to the Smoky Mountains, where we resolved the long-standing feud between the Hooffields and the McColts.  I had to use an extra powerful immobilizing spell on the arguing ponies to get them to listen to Fluttershy’s account of how the feud got started.  I know all of this, because I was there!”
At this, Left Head lifted herself and narrowed her eye at her twin.  She fired up her horn, and used her magic to spell out a challenge: POINT HER OUT.
“That’s not fair,” Right Head protested.  “You stole the images of my friends’ faces from my mind when you attached yourself to me.  I’d cast you out with my magic, but you stole my horn too!”
HORN’S MINE.  I’M TWILIGHT.
“No, I’m the real Twilight Sparkle.”
LIAR!
Twilight’s two heads snarled at each other.
“I got nothing,” Rainbow admitted.  “I thought it was Lefty, but Righty seems to know all about our adventures, and all about us.”
“Yes,” said Rarity, now that she had recovered, “but Right Head doesn’t recognize our faces.  She only knows that she is friends with Fluttershy, but she wouldn’t be able to pick her out of a crowd.”
“Does anypony else think it’s strange that only the right head can talk?” said Applejack.  “For that matter, how come the right head doesn’t have a horn?”
“I think I know,” said Fluttershy.
“I just wish I knew which Twilight was the real Twilight,” moaned Pinkie Pie.
“I know who the real Twilight is,” said Fluttershy.
“I don’t think either one of them is really our Twilight,” said Rainbow Dash.  “Each one is missing something from her brain, something the other Twilight has.  It’s almost like Twilight’s brain was…”
“…split in half?” Fluttershy interrupted.  Everypony turned to face her.  “That’s because it is.”
“What do you mean, split in half?” Right Head asked.  “If my brain were cut in half, there wouldn’t be two of me walking around, would there?”  Left Head shook her head in agreement.
“Actually, it is possible for a pony’s brain to be cut in half without any major damage to the function of the brain itself.” Fluttershy said.  She flew over everypony’s heads and pulled out a blackboard.  She picked up a piece of chalk, and started to draw while she explained.
“You see, your brain is divided into two hemispheres, left and right.  Each hemisphere does half the work of being your brain, and each hemisphere has its own specialized functions.  There’s a bundle of nerves called the corpus callosum that connects the two hemispheres together, so they can communicate with each other.  If the corpus callosum is removed, or severely damaged, the two hemispheres will continue to function normally.  They just won’t be able to share their information.  I think that’s what’s happing with Twilight’s two heads.”
Fluttershy flew back over to Twilight.  “The part of a unicorn’s brain that controls her magic is located in the right hemisphere, which is why this head has a horn, and can use magic.  Although the left hemisphere doesn’t have magic, it does have the speech center of the brain, which is why only this head can talk.”
“So, wait, let me get this straight,” said Applejack.  “Are you saying both of them are the real Twilight?”
“In part, yes.  Each has a piece of Twilight’s brain, enough to convince herself that she is the real Twilight Sparkle.  And yet, neither of them is the real Twilight.  The Twilight we know has control of both halves of her brain.”
“That…actually makes a lot of sense,” said Right Head.  “It certainly makes more sense than some strange creature from another dimension attaching itself to my body and pretending to be me.”
Left Head shook her head to disagree.  I KNOW WHO I AM, she wrote in the air.
“I think Fluttershy is right,” Rarity said.  “But there’s still one thing I don’t understand,”
“One thing?” Pinkie Pie interrupted.
Rarity continued, “How in Equestria did this happen to Twilight in the first place?”
Fluttershy shrugged.  “I’m not sure.  But if I had to guess, I’d say it’s some kind of magic that did this.”
“If it was,” said Right Head, “then it had to have happened last night, while I was asleep.  That was the last time my brain was whole.”  Left Head turned and gave her twin a disgusted look.  YOUR BRAIN?
“Listen, um, left hemisphere Twilight,” said Applejack.  “I’m no brain surgeon, but I think you are the one who remembers things that happened to Twilight.  So, why don’t you tell us what happened last night, so we can figure out what led up to…uh…this?”
Right Head narrowed her eye, and massaged her temple with her nearest hoof.  “Last night, I was up late right here in the library, preparing a seating arrangement for next year’s Grand Pony Summit.  Since it was the first year we would have a delegation from Yakyakistan, it was especially tricky to sort out.  You know how persnickety those yaks can be.
“Anyway, I was exhausted, so I fell asleep right there at the reading table.  That’s where I woke up this morning.  The first thing I noticed was that the world looked like a picture in a museum.  Like, I knew there was depth, but I couldn’t perceive it.  I tried blinking my eyes one at a time, only to find that I couldn’t.  I reached a hoof to my face, and that’s when I found out I only had the one eye.  So I screamed.  Then I heard another scream, similar to mine, but with a slightly different timber.  That’s when I saw her for the first time.”
“Wait a minute,” said Rainbow Dash.  “I thought the right brain couldn’t speak.  So, how was she able to scream?”
“Screaming is an emotional response,” said Right Head.  “Both halves of the brain can process emotion, and react emotionally.”
“Oh,” said Rainbow Dash.
“Do you think Twilight could have done this to herself?” asked Applejack.
“That is a possibility,” Rarity said.  “However, I think this spell was most likely cast by a different unicorn.  Somepony powerful enough to cast a transformation spell.  Somepony who has a history of casting spells on her friends.  Somepony who was inside the castle all night.”
“Starlight Glimmer!” said everypony all at once.
“I don’t understand,” said Right Head.  “I thought she learned her lesson.  I thought she knew better.  Why would she do this to me?”
“Here’s a crazy idea,” said Applejack.  “Why don’t we ask her?”
“She’s probably still in her bedroom sleeping,” said Right Head.  “Oh, shoot!  I don’t remember where her room is.”  Twilight’s left front hoof shot up unexpectedly, and started waving wildly.  “But, it seems my other half does.”
With Left Head taking the lead, Twilight took off through the library, down the hallway, up the stairs, and down another hallway to Starlight’s closed door.  Although each of Twilight’s heads could only control half her body, they managed to coordinate themselves well enough to navigate the castle without any difficulty.  The other ponies and Spike followed the two-headed Twilight.  They caught up just as Twilight knocked on the door.
“Starlight?” Right Head called out.  “It’s me, Twilight.  I need to talk to you about something that happened last night.  May I come in?”  There was no answer.  Twilight pushed against the door with her left front hoof, but it didn’t budge.  She tried turning the knob, but it wouldn’t turn.  “It’s locked,” she observed.  No sooner had she said that than Left Head fired up her horn.  She wrapped her magical aura around the doorknob, and it started rattling.  The sound of pins sliding through tubes could be heard as she worked on the knob.  Suddenly, the door swung open.  Right Head turned to her twin with a look of shock.  “How do you know a lock-picking spell?” she asked.  Left Head tilted her head, and shrugged her shoulder, as if to say “Beats me.”
Starlight was sound asleep in her bed, as was evident by her snoring.  The cover was pulled up to her neck, and she faced away from the door.  Twilight trotted in, and used her magic to rip the cover off the bed, expecting the sudden exposure to the cold air to rouse Starlight.  Starlight’s body twitched reflexively, but there was no sign she was awake.  Twilight’s right head nudged Starlight’s body, in an effort to wake her up.  Her left head followed suit, even going as far as poking her with her horn.  But Starlight kept snoring through all of that.
“This is Starlight Glimmer, right?” Right Head asked her twin.  Left Head nodded.  That little detail confirmed, Right Head turned back to Starlight.  “Starlight Glimmer, you wake up this instant!” she bellowed.  “I am your teacher and your princess, and if I say I need you awake, you had better be awake!”  Hearing this, Left Head turned to get a good look at her side.  She seemed surprised to find a wing there, and curiously prodded it with a hoof.  Her face twisted into a grimace that seemed to say “When in the blue blazes did this happen?”  And still, Starlight Glimmer did not stir.
“Step aside, Twilight.  Both of you, I mean,” said Rainbow Dash.  “I got this.”  Twilight did move to one side as Rainbow flew into the room.  She positioned herself above a small spot on the mattress that wasn’t covered by Starlight’s body.  Then, she folded her wings, and let herself drop back legs first onto that spot.  The bed gave a little under her weight, while the rest of it flexed upward, launching Starlight a few inches into the air.  Rainbow started jumping up and down on that same spot, causing the bed itself to squash and stretch in alternating waves, which bounced Starlight up and down.  Somehow, Starlight managed to stay sleeping through all of that.
Finally, Rainbow flapped over the bed, and let it settle.  “Nothing!” she said, dejectedly.  “Are we sure she isn’t dead?”
“She’s snoring,” Fluttershy pointed out, “which means she’s still breathing.  So, no, not dead.”
Left Head raised a hoof to tap Right Head on the muzzle.  Once she got her twin’s attention, she tapped her horn, then pretended to fall asleep, then pointed to Starlight.  “You really think so?” asked Right Head.  Left Head turned to Starlight, and passed her aura through Starlight from horn to toe.  Then she turned back to her twin and nodded.  “Of course!” said Right Head.  “Starlight must be under a Good Night sleeping spell.  She won’t wake up for anything until the spell runs its course.”
“How long does that take?” asked Applejack.
“Usually eight or nine hours,” said Right Head, “but the spell can be modified to last as long as a week.  There’s no way to tell how much time is left on this spell.  But even if there was, I’m not in the mood to wait for her to wake up.  We have to break the spell.”
“It’s too bad we don’t have her true love here,” Pinkie Pie said.  Then she gasped.  “Hold that thought.”  She took off with alarming speed out the castle door.
“What do you suppose she’s up to?” Applejack asked nopony in particular.
“It doesn’t matter,” said Right Head.  “My other head’s got this under control.”
Left Head nodded.  She fired up her horn, and directed magenta magical energy toward Starlight’s body.  The magic lifted Starlight into the air, and started poking and prodding at her eyes, her ears, her brain, and everywhere else.  But the magic bounced off the sleeping unicorn, with wildly wavy tendrils that dangled limply.  Left Head grunted as she strained to keep the magic going.  But it was no use.  With a defeated sigh, Left Head dropped her spell, and Starlight with it.  She snored loudly, letting the whole room know that the spell had failed.
Right Head covered her eye with a hoof.  “You were supposed to undo the spell she was under,” she said, “not cast a new spell with the opposite effect!  Spells like these don’t cancel each other out.  Don’t you understand that?”  Left Head turned away.  She would not meet her twin’s judgmental stare.
“Um, Twilight,” said Fluttershy.  “I don’t think you should yell at her like that.  She’s doing the best she can, considering she’s only working with half your brain.  You should be more encouraging.  After all, we still need her to wake Starlight up.”
Right Head sighed.  “You’re right, of course.”  She pulled her twin’s muzzle to look her in the eye.  “You’re not stupid, I know you’re not.  You know what you have to do, right?”  Left Head shook her head no.  Right Head motioned for Left Head to bring her ear to Right’s mouth.  Right Head whispered something.  Then Left Head nodded in understanding.
She walked up to the bed, and turned Starlight to face her.  Her aura reached into Starlight’s brain, and pulled out a cubical mass of turquoise energy.  Then, the tendrils of her magic started to trace along the edges of the cube.  The cube started to shrink, as parts of it peeled away and vanished.  Eventually, the whole thing was completely gone.  Starlight Glimmer’s eyes tensed, like she was trying to shut them even tighter.  Her snoring stopped, and she licked her lips.  She reached for a cover that was no longer there.
“Starlight, get up,” said Right Head, firmly but not loudly.
Starlight groaned in protest.  “Ten more minutes, Twilight.  I was having a really good dream.”
“This really can’t wait,” said Rainbow Dash from overhead.
Starlight opened her eyes.  She propped herself into a sitting position on her bed, and got a good look around her bedroom.  Almost all her friends were there.  She saw Twilight, her head divided into two heads, each head staring at her in anger.  Starlight recoiled.  Her eyes shifted as she pieced together what this was about.
“Okay, I know how this looks,” Starlight said.  “But I can explain.”
“Oh, this should be good,” Right Head snarked.
“Last night, I saw you stressing out over some paperwork or something,” Starlight began.  “I didn’t know what it was, but I figured it had to be something important if you were doing it yourself.  Anyway, it looked like you were having a hard time with it; I’m pretty sure I heard you moan with frustration once or twice.  But I distinctly heard you say this: ‘I can’t do this by myself.’”
“Is that what this is?” Right Head asked.  “Some botched duplication spell?”
“No!” Starlight protested.  “Let me finish.  I know, from Pinkie’s Mirror Pond debacle, that making copies of oneself almost always leads to an existential crisis of some kind.  Besides, you didn’t need to be in two places at once, you just needed another brain in the same place that you already were.  So, I did a little digging in the library, and I found this transformation spell that said it would give you a second head.  I thought it would give you two brains to work on your problem, I didn’t think it would split your head in two.”
“Did you read all the directions on that spell before you cast it?” asked Right Head.
Beat.
“No, I didn’t,” said Starlight.  “And now that you mention it, I think that might have been part of the problem.”
Right Head groaned, and held her face in her hoof.  Left Head just glared at Starlight, shaking her head.
“Didn’t you learn your lesson the last time you used magic on your friends?” Applejack shouted.
“How many more times are you going to make the same mistake?” added Rarity.
“Is magic just your answer for everything?” asked Rainbow Dash.
“I deserve that.  All of it,” Starlight said somberly.  “I guess I still have a lot left to learn.  Twilight, I’m really sor…”
“Don’t say a word,” Right Head cut her off.  “You’ll have plenty of time to apologize after you fix this.  Now, come on.”  Twilight trotted to the door, before she realized that Starlight wasn’t following her.  First Left Head, then Right Head turned back to look over their respective shoulders.  “Well?”
“Oh, you mean, right now, right now?”
Right Head rolled her eye.  “No, I thought I’d take a lap around Ponyville so its citizens could gaze upon the Princess of Polycephaly.  Yes, right now!”  Starlight obediently followed after her teacher.
“Princess of Poly-what now?” asked Applejack.
“I don’t have time to explain!  Look it up!”
Twilight and Starlight galloped downstairs.  When they reached the bottom, they were greeted by Pinkie Pie at the front door.  She was accompanied by an orange and white unicorn stallion, with a familiar set of eyeglasses.
“Hey, Twilight, and other Twilight,” Pinkie Pie said.  “Great news!  I went to the Crystal Empire, and I brought Sunburst back with me!  Now, he can give Starlight true love’s kiss, break the sleeping spell, and wake her up!  Oh, hi, Starlight.  Nice to see that you’re awake.”  Pinkie’s eyes narrowed to pinpricks when she realized what she just said.  “Oh, come on!” she shouted to the heavens.
“P-P-Princess?” Sunburst stammered when he saw the state Twilight was in.  “What in the world happened to you?”
Right Head turned to her twin, and asked “Have we met this pony?”  Left Head nodded.  Right Head turned back to Sunburst and sighed.  “You want the long version or the short version?”
“I can see you’re in kind of a hurry here, so, short?”
“My student doesn’t know how to read spell books.  That’s what happened.”
“Now, wait a minute,” Starlight began, “I don’t think that’s quite fair…”
Right Head cut her off.  “I believe I said you could speak again when my head is whole, did I not?”  With that, Twilight went to the library.  Starlight followed, as did Sunburst.  Left Head started using her horn to pull many books from the shelves, and started opening them for herself and Right Head to read.
“I still don’t understand,” said Sunburst.  “What spell did you cast on Twilight?”
“It was Mage Moreau’s Double Header spell,” said Starlight.  “I thought it duplicated the head of the target, resulting in two whole brains.  But apparently, it separates the left and right hemispheres of the brain into two smaller skulls.”
“So, Twilight has a split brain now?”
“More like a split head.  But yeah, pretty much.”
“I think I remember researching Moreau’s work,” Sunburst said.  “He was a key pioneer in transformative spells.  Bit of a nutbag, too, but that’s beside the point.  Anyway, you’re right; his Double Header spell should result in two whole brains, not two half brains.”  Sunburst adjusted his glasses.  "Why were you trying to give her a second head in the first place?"
Starlight blushed.  "You don't want to know.  You'd only think I was being silly.  And you'd be right."
“Aha!” said Right Head, when she saw what she was looking for.  She pointed this out to her twin, who levitated the book over to Sunburst.
Sunburst adjusted his glasses, and took the book in his own magic.  “Oh, I see the problem.  This spell is an earlier version of the Double Header spell, a rough draft, if you will.  He later combined this spell with a mild duplication spell, which produced the result he was seeking.”
“Well, that’s very interesting,” said Right Head, “but now that we have the spell Starlight used, we can just undo it, right?”
“I’m afraid it’s not that simple,” said Sunburst.  “If this spell cut the wire that connects your two hemispheres, reversing it isn’t going to bring that wire back.  You’ll have one head again, but your brain will be forever split in two.”
“Well, that’s no good,” said Right Head.  “The Princess of Friendship should be able to recognize her friends’ faces.”  Left Head turned to look at the wing on the other side of her body.  Then she turned to look at Starlight quizzically.
“There is an alternative solution,” Sunburst said.  “You see, Moreau’s work included some spells that merge two conscious beings into one consciousness.”  He flipped through the pages of the book he was holding.  “It won’t be the same as restoring your brain to its original state, but it should be a close enough approximation.”
“What have I got to lose?” sighed Right Head.  Left Head did not react.
Starlight took the book from Sunburst, and quickly read through the instructions.  Not too quickly, she made sure to read all the instructions.  She fired up her horn, and wrapped her turquoise aura around Twilight’s two heads in a figure eight pattern.  She duplicated the pattern twice, then started to slowly tighten the circles she was making.  Right Head, for her part, moved herself closer to Left Head, until the two of them touched.  The magic kept sliding in between them.  Starlight started another trail of magic, this one circling both Twilight’s heads in a single loop.  It completed five circuits, completely engulfing the two heads in turquoise light.  With that, Starlight cut the flow of magic from her horn.
The light surrounding Twilight disappeared, revealing that the spell had failed.
“What?” Starlight said.  “I don’t understand, I followed those directions to the letter!”  She turned back to the book, and quickly scanned the page.  “Uh-oh, I think I see the problem.”
“What is it?” asked Right Head.
“This spell will only work if both the participants are willing to be fused together.  If one or the other is resisting the spell, it will never work.”
“That can’t be it,” Right Head protested.  “I’m more than willing to get back to normal, and so is she.”  She turned to face her twin, “Right?”  Left Head bit her lower lip, and turned her eye away from her twin’s gaze.  But the fact that she didn’t nod right away told Right Head all she needed to know.  “Unbelievable!  What possible reason could you have for not wanting to go back to the way things were?”
Left Head sighed, and used her magic to spell out: I DON’T WANT TO DIE.
“You’re not going to die,” Right Head said.  “You’re going to rejoin me, and we’ll have a whole brain again.”
I AM WHOLE, Left Head wrote.  I AM TWILIGHT.
“No, you’re not,” Right Head countered.  “You’re only a fraction of the real Twilight Sparkle.  You need to merge with me to become whole again.”
Left Head blinked back the tears that were starting to form.  I’LL BECOME YOU.
“What is that supposed to mean?”
“Twilight, shut up!” Starlight Glimmer said, surprising even herself.  Right Head looked back at Starlight and narrowed her eye at her.  “I mean, you’re not going to get anywhere by yelling at her like that.  Look at her, can’t you see that she’s scared?”
Right Head shot a glare at her twin.  Even though she wouldn’t meet her gaze, she saw Left Head wipe a tear away from her eye.  She didn’t fully understand what that meant, but from the way this pink pony was yelling at her, Right Head knew something was wrong, and she was the cause of it.  With this thought, Right Head closed her eye and remained silent for a while.  When she spoke again, her voice was quieter, softer.
“Twilight,” she began, facing Left Head, “I’m sorry.  I didn’t mean to belittle you.  I was only yelling because I was frustrated.  But the truth is, I need you.  I want to be able to recognize my friend’s faces again.  I want to remember where I put things again.  And I want to be able to do magic again.  But I can’t do any of that without you.  Without you, I’m not truly me.”
Left Head wasn’t buying any of her twin’s half-hearted apology.  She didn’t truly understand how she felt.  She was just buttering her up to get her to agree to the merge.  Left Head didn’t need this over-bearing control freak messing up her life, even if she was a part of herself.  She turned away from her other head in disgust.
That’s when she saw her wing for the third time that day.  It occurred to Left Head that her twin wasn’t fazed by this; in fact, she frequently referred to herself as a princess.  But the revelation shocked Left Head each time it happened to her.  How had this happened to her?  She didn’t remember, but clearly Right Head did.  Now that she thought about it, how did she know she could trust Starlight Glimmer and Sunburst?  She recognized their faces and names, but she didn’t recall anything about them, or even how she met them in the first place.  But Right Head did know these things.  These things that she, as Twilight Sparkle, really should know.  It hurt to admit it to herself, but her other head was right.  Without her, she wasn’t truly herself.
Left Head turned back, and saw her twin hang her head in shame.  She saw a single tear escape from her single eye, and knew what she had to do.  She nuzzled Right Head’s neck, softly and slowly, to get her attention.  When her twin looked back, she smiled at her warmly, then simply nodded her head.  Right Head smiled back as the tears started to form again.  She opened her mouth to speak, but stopped herself.
“Thank you.”  Those would end up being Right Head’s last words.
Twilight’s two heads turned to face Starlight Glimmer.  They nodded together.  Starlight smiled, and lit up her horn to try the merging spell once more.  Now that Left Head wasn’t resisting, the spell had its intended effect.  It felt like Starlight’s magic was peeling away the layers that separated the two heads.  Fur was stripped away.  Then skin, then flesh, then bone.  A shock of cold met each head on the side facing her twin.  She could feel a strange energy coming from that side.  She was drawn toward it.  She shuddered as the energy intensified.  She shut her lone eye.  She drew closer.  She bumped against her other head.  Her other head attached to her.  Her muzzle twisted in the direction of the pull.  It shifted, and merged with her twin’s.
Twilight could feel both sides of her head again, as the spell continued to work.  Her forehead started to come together, and her horn moved to its proper place in the center.  Her muzzle, now one piece, shrank backward to rest comfortably between her two eyes.  A warm feeling replaced the chill of the castle air as the gap down the middle of her head sealed up.  Then, pain set in immediately.  Twilight’s memories started moving back and forth between the two hemispheres of her brain, and she could feel each one.  Thousands of faces, names, locations, events, emotions, lessons, and relationships raced across the landscape of her mind.  The thoughts were familiar, and yet alien all at once.  They carved deep trenches in her mind, indelibly marking each half of her brain with the essence of the other.  When the action quieted, Twilight opened her eyes.  After looking with only one eye for so many hours, the sudden 3D view afforded by binocular vision made her feel a little dizzy.
“Whoa,” she said.
“Well, she looks like herself at least,” Starlight said.  “Twilight, how do you feel?”
“I feel strange,” she answered.
“Strange how?” asked Sunburst.  “Do you at least feel like yourself again?”
“Yes,” Twilight said, “but I didn’t think coming back would feel like this.”
Starlight and Sunburst said nothing, silently prodding Twilight to continue.
“I thought that, once we fused, Right Head and Left Head would disappear, and I’d come back, with no memory of being two-headed,” she explained.  “Instead, I remember everything, from both sides of my head.  I remember feeling browbeaten by some pushy know-it-all.  I remember being the pushy know-it-all, and getting frustrated with my other half like she was weighing me down.  I remember panicking when I found out I had lost my horn.  I remember feeling helpless when I lost my voice.  In both instances, I hated the other me for taking something I thought was mine alone.  But, I guess it wasn’t really mine at all, was it?”  Twilight moaned, and held her head in a hoof.  “Oh, no, here comes the headache again.”
Starlight ran to her teacher and hugged her, stroking the back of her head.  “This is all my fault,” she said.  “This has to be way worse than the Mirror Pond thing.  I’m really sorry, I never should have used that damn spell in the first place.”
“It’ll be okay,” Twilight said, returning her student’s embrace.  “I’m not mad at you for this.  Your spell only separated the two hemispheres of my brain, it didn’t make them distrust each other.  That was my fault.  Our fault.  The point is, it’s not your fault.  All you really did was show me something that has always been the case.”
“What do you mean?”
“I mean, I have always had two minds living together inside my head.  Normally, they coordinate with each other so well, that they can present as a single entity.  But, given the right circumstances, my two minds can act independently, and can end up disagreeing.  My mind isn’t entirely mine.”
Just then, the rest of Twilight’s friends came into the library.
“Did it work?” Pinkie Pie asked.  “Is she better?”
“One way to find out,” said Rarity.  She sauntered up to Twilight, who turned to face her.  “Well, she’s got one whole head again.  Twilight, darling, do you recognize me?”
“Of course I recognize you, Rarity,” Twilight said.  “I also remember helping you organize your merchandise shipment for the grand opening of your boutique in Manehatten.”  Twilight smirked to herself.  “It was some of my best work.”
“Oh, thank Celestia!” Rarity said.  “Twilight’s back to normal!”
“Yeah, back to normal,” Twilight said.  But she wasn’t sure if she meant it.