“You cannot stop me, pony!” the tall Changeling shouted, exposing her fangs to the group of ponies in front of her.

“Of course I will. I always stop you, any of your kind. Any time a petty, selfish changeling princess like you try to take over a small, pony town like this just to spite her Queen, I´ll be there to stop you!” the brown pony with an hourglass Cutie Mark said.

“You have no rights! You are a stranger in this world! How dare you?”

“Oh, I dare. Watch me dare!” he shouted, making the monster back down. “I dare because I´m not supposed to be here but neither do you! You want to play by the rules? You want to follow the natural order? then fight your way in the Hive, raise from a drone into a Queen and then come face the ponies but, if you want to cheat your way to the crown by using these ponies as your tools then...well, here I am!”

The young, prideful changeling hissed. The brown pony kept his look gazed on the creature and then opened a box in front of him, releasing a storm of snow upon her and her army.

“What´s this?”

“Windigos in a box. Reminds me of an old legend. I guess there´s some sort of irony attached, an old fairy tale bringing the end of a prepubescent dictator. Just...irony.”

“No! Stop this, Doctor! It´s cold...too cold!” the Changeling shouted but the Doctor ignored her and opened the box some more, releasing more snow and wind.

“Doctor!”

The Doctor kept ignoring the pleas even when these pleas came not from the changeling but from a pony behind him.

“Doctor, you´re killing her! Stop!”

He kept looking straight at the Changeling, watching her freeze and crumble. At his back, five ponies stood in terror, covering their mouth with their hooves or trying to look the other way. One pony however watched, she watched with her mismatched eyes at the pony in front of her committing the most despicable act she could think off.

“Doctor, please! You already won! Let her go!”

He kept looking, never taking his gaze away. Not even blinking. Just starting at the fragile wings turn into ice and break, the glowing black horn turn white and the jaw froze in an agony scream.

He kept watching the entire time.

*****

“Is there any way to stop him? Any spell that can reform him?” Derpy Hooves asked the Princess.

“That´s not how the reform spell works, Derpy. It brings forwards the natural good instincts of a creature, removing all the vile magic that could be corrupting it. The Doctor...may be extreme but his heart is in a good place. His two hearts,” Twilight explained.

“He shouldn´t be here. He is no different to the monsters he fights,” Derpy said.

“Derpy, he´s…”

“He must be stop, Princess. You must stop him before...before he…”

Twilight approached Derpy and placed a hoof on her shoulder. “I know you´re worried about him, Derpy. He´s a little unpredictable but he´s not a stranger anymore. He belongs here now. He already explained to me why he can´t never change back to a human. He´s forever a pony now, an unusual type of pony. Besides, you don't really want him to go, right?” Twilight said with a smile but Derpy didn´t smiled back.

She kept her head low and when the Princess turned her back, she looked with her two eyes focused to the stand with the Elements of Harmony.

*****

“It´s...magnificent, “ Trixie said, holding the Crown with her hooves.

“Derpy, are you sure about this?” BonBon asked the grey pegasus.

“Yes. It´s for the best,” she answered, handling the candy maker Fluttershy´s Element.

“I believe she was referring to her being here, “ Octavia said, nudging to Trixie while she tried to adjust the balloon shaped necklace to her neck.

“Yeah, why do you bring her when you already have two cool unicorns?” Vinyl said, taking off her glasses.

“Because neither studied at Celestia's academy. Trixie knows how to handle magical items,” Derpy explained.

“Yeah, I remember how well she handled the Alicorn Amulet,” Lyra sarcastically replied.

“Hey, I...I mean, the Great and Apologetic Trixie has been studying a lot since that time. I bet that she can even handle the Alicorn Amulet now!” Trixie said, blushing offended.

“We need her,” Derpy said, putting on Rainbow Dash´s necklace.

Reluctantly, Lyra and Vinyl put on the orange and blue necklaces.

“Aside from Trixie´s questionable talent, there´s a more important point. We´re not the Element Bearers, how are they going to work?” Octavia asked.

“WIth that,” Derpy said, pointing at the blue box in the middle of the field.

By all accounts, it looked like a simple blue box but it was more than that. The way it stood in the field, like a second picture attached to a photograph, sticking out; it wasn't something born in Equestria. It looked like it but it didn´t belong.

“How exactly?” BonBon asked.

“It´s a magic conductor,” Trixie said. “This...box.”

“The TARDIS,” Lyra interrupted her.

“Yes, that. It´s a source of magic, one that I can´t quite identify but it´s powerful. While it´s true the Elements won´t answer to us they're still magic items and they resonate when exposed to a magic source like a spell or this box.”

“The TARDIS,” Lyra and Vinyl said.

“Yes. So when I activate the spell, the Elements will resonate with the box…”

“TARDIS!”

“I get it! I get it! The box will resonate with the Elements and the spell will work!” Trixie yelled.

“What spell?” BonBon asked.

Trixie looked at Derpy who was looking at the closed door of the TARDIS.

“A Cutie Mark removal spell,” she said.

*****

BonBon kept the unconscious Doctor close. She knew she had no chance of stopping the guards but she wasn´t going to go out without a  fight. Lighting Dust descended in front of her and she hugged the Doctor closer. Jay-Jay flew over to the pegasus and pick her snout. Lighting Dust was quite obviously angry backed down while Trixie pushed her aside with a wing.

“Move,” she ordered BonBon but the earth pony didn´t move.

Trixie nodded to order the guards to separate both ponies but suddenly a bright, purple flash hit them and Twilight Sparkle materialized in between the alicorn Princess and her prisoners.

“That´s enough, Trixie.”

“How can you remember? You were not supposed to remember!” Trixie yelled.

“I´m a Princess and the Bearer of the Element of Magic. I´m the central focus of the Elements, of course the spell wouldn't affect me,” Twilight explained.

“No, Im a Princess now! And I´m not going to let you take this away from me!”

“You are letting your pride take the best of you again, Trixie. Look around, look at how much the world has changed because of your actions,” Twilight said, pointing at the dark clouds above their heads. “Our actions. I let this happen, thinking it was for the best but I forgot that there are consequences for every action. Like a pebble in a pond, this is what we caused.”

“No, itps..it´s his fault! He shouldn't be here!” Trixie said, pointing at the Doctor. “I took away his Cutie Mark, his destiny. He no longer has a place in here.”

“We made a mistake. His destiny is tied to that magic box…”

“The TARDIS,” BonBon interrupted her.

“Yes, that box and the Doctor are tied, it´s oart of his destiny. The spell tried to expel him but the box refused to let him go, it can't leave. And the effect of its presence here are spreading,” Twilight said.

Lighting Dust and the guards were as confused as BonBon but she was waiting to see what will Twilight or Trixie said next. The winged unicorn sighed and said, “What should we do then? How can we fix this?”

“I don´t think it´s up to us…” Twilight said.

****

“Why is it railing?” Vinyl yelled, trying to get a hold of a railing.

“I believe the correct question is how is it shaking bein a box biggen on the inside and,,.”

“SHut up, Octavia!”

“She´s in pain! Something is hurting her!” Lyra yelled and looked at Derpy, who was pulling levers and pushing buttons on the console.

“I´m sorry,” the pegasus murmured to the console pushing a big red button causing the entire structure to tremble.

“Derpy, what are you doing?”

“Fixing my mistake. The Doctor taught me how to operate the TARDIS and I can sent it away from Equestria. If I remove the connection it has with the Doctor, the spell will finally work and he´ll turn into a common pony. This time it will work,”

“What spell? What is she talking about?” Vinyl asked.

“Well, if you ask me…” Octavia began but then she noticed Vinyl´s expression. “Nevermind.”

“You knew him. You remembered him all along,” Lyra said but Derpy kept quiet. “You did this, you changed our destinies, swapped our Cutie Marks..”

“It was an accident! The spell was supposed to remove him of his Cutie Mark and changed into a regular pony. Take away...all of this,” Derpy explained, waving at the large buzzing console.

“I remember. I remember the TARDIS disappearing and going back, the Doctor returning for a trip…” Lyra said.

“Hey, I remember too. I was there and you were there,” Vinyl said, pointing at Octavia. “We were trying to do something.”

“You were whelping me. Helping me stop the Doctor. Stop him before he did something horrible again,” Derpy said.

“I remember...being so scared of him. Scared of what he is,” octavia said.

“That´s why you did it, right Depry?” Lyra said, using the railing to help stand up. “You didn´t want anypony else to be scared of him. You didn´t want to be scared of him anymore.”

“I just...I just wanted him to stop running…”

“Oh, you are not the first, my dear Derpy.”

They all turned to look at the door and saw the Doctor coming in helped by BonBon.

“Doctor!” Derpy said, unable to hold her feelings.

“But I´m afraid that…” And the Doctor opened a box that was on the ball and pulled a switch. Immediately, the lights went back to normal and the room stop shaking.

“Is that it?” Vinyl said, apparently disappointed the dramatic moment was finished by simply pulling a switch.

“Well, that takes care of that. What was I saying? Oh yes, I´m afraid that Is till have a little more of…” And he didn't finished the sentence because he fainted, again.

Lyra, Vinyl and Octavia rushed to his side. BonBon looked at Lyra, silently asking for help and the mint unicorn nodded. Behind them, Derpy Hooves fell to her haunches, tears finally set free.

*****

Lightning Dust hadn't understood a single thing of what was going but she was actually a simple pony who liked simpler things. When it come to flying, she simply went faster and higher. And when it comes to magic matter, she just let them on Trixie´s hooves. She trusted the Princess and wasn't a pony that would question Royalty so she was quite nervous when Trixie ordered her to sent the guards away and asked them to keep a perimeter around the blue box that had appeared on the city park. The guards weren´t exactly pleased since they had orders to capture the palace trespasser but they obeyed. Lightning Dust also managed to dismiss the royal servant that came directly from Princess Celestia, ordering Trixie to come back to Palace. While the unicorn didn't quite believed the story that Trixie was performing a magic experiment that required her full attention, she still retired, promising to come back with a captain of the Guard.

Lighting Dust and looked behind her at the blue box that seemed to concentrate all the unnatural dark clouds that loomed over the city. She really didn't understood what was going on but hoped that Trixie could fix it.

Trixie and the others were surrounding the Doctor, who kept going in and out of consciousness. The worried little blue phoenix was resting on Octavia´s who immediately took a liking to it.

“I just...I just wanted to prove that I was talented. That I could handle the Elements of Harmony just as well as you,” Trixie said, not daring to look Twilight at the eyes.

“I understand, Trixie. Like I said, this is also my fault. Byt the time I noticed that Derpy had stolen the Elements, it was too late,” Twilight said and everypony looked at Derpy who was still sobbing. “I woke up in Canterlot, knowing exactly what had happened.”

“Then why didn´t you tried to change it back? Why did you keep the secret?” Lyra asked her.

Twilight took a moment before answering. “When Trixie connected the Elements to the…” And Twilight looked at BonBon before continuing.

“TARDIS.”

“Yes, I felt it. Something...something deep, like an ancient type of magic.”

“What is it?” Trixie asked.

“I´m not exactly sure but it´s what makes the Doctor special and it´s exactly why we can´t change him.”

They all looked again at Derpy who was looking at the Doctor.

“I asked him. I asked him by he didn´t stop, why he didn't let her live. He told me…” And Derpy needed a pause before continuing. “He told me that everything has its time and place, that he was there because he needed to stop her. But, who´s going to stop him?”

“Well, I´ll say we already got our answer…”

“Doctor!”

The ponies rushed next to the Doctor who, despite the circumstances, was smiling.

“Doctor, I didn´t mean to…”

“Shh, it´s okay Derpy. No need to be sad. Remember what I told you, everything has its time and place and it seems mine…” And he winced in pain. “Mine is running out.”

“I can fix it! I can reverse the spell and change things back before it´s too late! Our memories are still intact, Twilight´s, Derpy´s and mine. Even they remember enough about you to bring you back and restore the balance!” Trixie rushed to say.

“That´s all nice and soun, except for one things...I don´t want to come back.”

“But Doctor…” Lyra said but the Doctor interrupted her with a hoof.

“Listen, I am an intruder. I don´t exactly belong here and trying to fix the mistake I am, caused this whole mess. It´s not just that your lifes changed but your swapped destinies are starting to resonate with the other ponies, with the entire kingdom. This is not how things are supposed to be, not how they work AH!”

“Doctor…” Derpy said and placed a hoof on his face.

“Don´t cry, my dear Derpy. I don´t like watching you cry…”

Derpy broke in tears and the others ponies were struggling with their own. Trixie looked at Twilight and she nodded. Trixie lightened her horn and the magic started flowing from her to the TARDIS and then it distributed among the other ponies.

Lighting Dust watched from afar as a rose glow rose from the spot the Princess were and as it grew, it slowly changed colors to purple. The glow engulfed the entire city and exploded, magic coursing through all of Equestria. Lighting Dust blinked and looked around, wondering why she was in Canterlot. Shrugging, she simply took off and flew back to Cloudsdale.

Trixie opened her eyes and saw Twilight spreading her wings.

“Glad to see you back, princess. Think you can forgive me?”

“I already have, question is if you can finally stop trying to prove that you´re better than everypony else. Just be proud of you are Trixie, instead of constantly looking for an easy opportunity,” Twilight said.

Trixie didn´t answered, just lowered her head.

“Alright, my Cutie Mark is back!” Vinyl Scratch loudly announced. “So it´s yours! And yours! And yours! And..”

Derpy wasn´t even listening to her. She was still crying over the cold, immobile body of the Doctor, her eyes having returned to being out of balance.

“He didn't make it,” Lyra sentenced.

A minute of silence passed by before they heard the loud chirp of a bird.

“Jay-Jay?” Lyra asked, watching the blue bird posing over the Doctor.

“Could it be?” Trixie asked.

Octavia was tempted to ask what but she kept her mouth shut.

“Could it be waht?” Vinyl asked and Octavia rolled her eyes.

“A blue phoenix it´s a creature of legend. It is said that they no longer exist on Equestria but there are tales of yore, of the blue birds that brought life,” Trixie began.

“Look,” BonBon said and they all looked at Jay-Jay starting to glow, her light transferring to the Doctor.

“For you see, while a red phoenix can return from its ashes…”

And Jay-Jay exploded in a flash of light, its final song dedicated to the Doctor.

“A blue phoenix gives its life to others,” Twilight finished.

The ponies watched in awe as the Doctor body trembled and changed. They watched his body shrink and a horn form on his head. When it finished, a completely different pony was in place of the Doctor.

“Good gracious! That was quite a nap!”

The unicorn looked at the dumbfounded ponies with their jaws open.

“What? Is there something on my face?

*****

The Doctor inspected his new body on the mirror. Actually it was HER new body now. She looked at the light blue coat and the white and dark blue mane. She inspected her horn, not quite sure how to use it yet. She lciked her tetther,s marvleing at how white they were. She then took a good look at her rump, giggling.

“Well, it´s good to see some things never change.”

Giggling some more, she went downstairs. She passed by the console on the way out and patted the old machine.

“Ah old friend, we have been through some rough bumps in the journey, haven´t we?”

The machine seemed to respond, emitting a soft buzz.

“Now that I got a change of style, you should follow suit. Tell you what, I´ll take a little walk outside and in the meantime, you can redecorate. I was thinking something classic, like a doctor´s office. I think it fits me, right?”

Winking, the Doctor left the room, letting the TARDIS to work its mysterious magic. Once outside, the first pony she ran into was a pretty confused Vinyl.

“Yes?” the Doctor asked with the other unicorn just inches away from her face.

“So...you are the Doctor? Or is it Doctor-ess?”

“Vinyl please, that isn't even a real word,” Octavia said.

“What she said. And yes,” the Doctor said, pushing Vinyl aside. “I am the Doctor.”

“You are not the Doctor,” BonBon sentenced.

“I am the Doctor. I just regenerated.”

“Regen-what?” Lyra asked.

“It´s a process that my species has. When we´re at the brink of death, out entire cellular structure…” the Doctor stopped when she noticed the complete look of confusion on their faces. “Magic.It was magic.”

The other ponies seemed satisfied with the answer and nodded.

“Good thing it happened. I was convinced the regeneration process wouldn't work in this new body but, seems the sacrifice of my little friend gave my body the necessary energy to change me.”

“Jay-Jay…” Lyra said and Vinyl patted her back.

“You´re still not the Dcotor,” BonBon isnsited.

“For the last time, I am the Doctor. I´m just a mre now which is, admittedly, an unusual feeling. I always wondered how it will be to regenerate into a woman. Never got a chance with my old body. Well, bodies actually.”

“This has happened before?” Octavia asked.

“A couple of times,” the Doctor dismissed the issue.

“No. I mean that you´re not the Doctor. I know this pony, this pony you turned into,” BonBon explained. “Her name is Minuette, she helps in the Hospital in the weekends.”

“Oh yeah, I know her too! She used to live in Canterlot!” Vinyl said.

“I did?”

“I seem to recall somepony similar as well,” Octavia said.

“Yeah, I think Ié saw her around town too,” Lyra added.

“Okay okay, this is important. Tell me more!” the Doctor said, pulling a notebook with her magic.

“Wait. How come we know you before today? that doesn't makes sense!” Vinyol said.

“Oh, it makes perfect sense. You haven't met me yet. i mean, you will. I mean, I need to come back in time and be there so you can meet before you meet me like I was before and...agh! this notebook keeps slipping! How do you hold things with magic? It´s more complicated than doing it with a horn!” the Doctor complained and the other ponies laughed.

“I don´t see what´s so funny about it…” the Doctor murmured and then she noticed Derpy Hooves approaching them. “Derpy?”

“You are still here,” she said.

“So it seems.”

Derpy smiled.

“Well, not me precisely. Not the old me,at least. Is this new me that it´s still pretty much the same me as before. Minus the gender and the coat and the mane and horn and teethes...Cutie Mark is still the same. Seems I´m a bit undecided on this incarnation, can't keep a thought straight. It´s gonna take a while getting sued too.”

“...yeah, I´m not sure which version of you was more annoying,” Vinyl said, causing the Doctor to frown.

“Does this means that you´re leaving?” Derpy asked.

“I guess so. I´m a new pony now, a new mare. I want to explore this new me. New body, new TARDIS. New companions.”

“Nw companions?” Lyra asked.

“They usually come with the whole package. Not necessarily, nothing says I can´t still travel with you, girls. But...I will understand if you don't want to come with me this time. I´ll understand if you don't want to come with me.”

They looked at Derpy, waiting for her answer.

“I want too but…”

“It's okay, Derpy,” the Doctor said, holding her hoof. “I understand.”

The TARDIS then called for the Doctor, the sound of its bells calling for adventure. The Doctor took a good final look at her friends, friends that she will never change one bit. She got a new opportunity, an opportunity to be with them without dragging them into danger. She already knew she had done it, she had managed to live a life as this pony Minuette for a while, hanging around with the other ponies. Now it was just a matter of figuring out how to do it.

Smiling, she rushed to the TARDIS. SHe stayed at the door, looking at the other ponies waving at her. The Doctor waved back and went inside the TARDIS, slowly fading away leaving a solitary leaf behind that floated in the air where a blue box used to be.