Regeneration

It seemed like forever ago when the Doctor saved Derpy from the living Plastic, or fought the lone Dalek in the secret base underground. It seemed so long ago. Now, Derpy was passed out on the floor of the TARDIS, recovering from absoring the Time Vortex. The Doctor had removed it from her by kissing her, and expelled it back inside the TARDIS, but at a cost. This body was experiencing Cellular Destruction.

The Doctor was at the controls of the TARDIS, aiming the course for present day orbit around Earth, just above Equestria. It reminded him of the time he and Derpy fought Lady Clarissa, the last pure pony, during the End of Earth, and the Second Great Equestrian Empire. Again, it seemed so long ago, yet it had only happened a little over a month ago. Or, in present time, it would happen in about 400 billion years.

Wibbly Wobbly Timey Wimey, the Doctor muses.

A sharp pain courses through his body. This body was a dark-lavender color, with a sharp red mane and tail. It wasn't his favorite body, but he likes the mane. Red is cool.

Derpy starts to wake up as another pain courses the The Doctor's body, causing him to straggle away from the controls, but manages to get back to them before Derpy is finally awake, and standing up. "... Doctor...?"

"Don't try to do anything too fast, Derpy. Your body is still recovering."

Derpy looks around to notice that they are back inside the TARDIS, safe and sound. "Where... The Daleks! What happened to them?! Are we safe?!"

"Yes we are, Derpy. The Daleks, well, to be blunt about it, you killed them. Every last one of them, POMPH! Up in flames! Vamoose! Gone!" The Doctor says with a huge grin on his face, but then, another pain courses through him, causing him to once again back away from the controls.

Derpy rushes towards him, but The Doctor backs away even more. "S-Stay back!" Derpy stops and backs away, and the Doctor starts to regain composure. "Ow... You know, it's sad really... There were so many places I wanted to take you, Derpy...

"The Shada Prison, The Ice Planets of the Gorgon Galaxy... All of these *Ack!* Fantastic places..."

"What do you mean?" Derpy asks the Doctor, not understanding the situation. What did he mean? Was he going away, dropping her off somewhere? Making her go back home? Was he... Dying?! All of these thoughts run through her mind as the Time Lord in front of her cringes his face in mortal pain.

"Doctor, what do you mean?"

The Doctor takes another breath and tries to regain his composure, but fails. "It... It means I'm not gonna see ya again... Not with this dafty old face..." The Doctor opens a weak smile, but it quickly goes away. The memories flood back to both The Doctor and Derpy.

The Daleks, the game shows, and the first time Derpy met the Doctor...

Derpy walks around the basement, looking for a light switch, or something to spread some light. She fails, though, and is forced to go in the Dark. She wanders about, looking for the mouse traps she was supposed to clean. A noise startles her. "Ah!"

She starts to run forward, away from the noise. She is suddenly cornered by... Envelopes for Mail? Whatever the cause for this, it scares her, so she cowers to the nearest wall. Suddenly, a Stallion is standing beside her, and taps her on the head.

"Run!"

So, that's what they did. They ran, evading Envelopes, and barrels, and other random things blocking the path. The Stallion leads Derpy to the front Door, where she promptly exits, but is stopped by the Stallion.

"I'm the Doctor, by the way. Who are you?"

"D-Derpy..."

The Doctor holds up a small bomb. "Good to meet ya, Derpy! Run for your Life!"

Then, Derpy barely knew the Doctor. She still barely knew him, but she loved him, so she kept trusting him with her life. Of course, Derpy knew that he probably didn't even know that she loved him, but she kept that one little spark of hope.

The Doctor was having the same memories. As another pain courses through his body, he remembers that he still needs to explain the process of Regeneration. "There's this... Process..."

"Doctor, what's wrong?!"

"This process means that..." The pain was  getting unbearable now, but he fought through it, for he knew that if she didn't know what happened, she may go crazy. He tries to form the next words, but his body fails him. He tried yet again, and again, and finally manages to form words.

"It means that I'm gonna change..."

The Doctor looked to the TARDIS console, and back to Derpy. She was on the verge of tears. The stallion, or alien, she loved was about to die. She didn't want to come to terms with that, but it was blatantly obvious that he was in excruciating  pain, but she fought to hold back the tears.

She failed.

The Doctor spoke yet again, using up more of his strength. "I'll still be here, but I won't be seeing you again with these eyes..."

"And before I go-"

Derpy interrupted him, crying her eyes out. "Don't say that!"

The Doctor cut her off. "And before I go... *Augh!* ... I just want you to know that you are Fantastic... Absolutely Fantastic!"

Derpy smiled for the first time since she woke up.

"And... do you know what?"

The Doctor smiled while he looked over her for the last time.

"So was I!"

The Doctor grins one of the biggest grins he ever had. He looks up into the ceiling of the TARDIS, and his face was covered in a gold aura. In fact, the same thing was happening to his whole body. His features morphed into another Stallion.

His coat was turning brown. In fact, his whole body was brown, including his mane and tail. Derpy was taken back by the gold light, and hid behind a pillar next to the entrance to the TARDIS. Soon, The Doctor was a completely different Stallion.

The gold light diminished into nothingness, and a brown stallion with blue eyes stands where the Dark Lavender on stood just seconds before. He looks around for a second and turns to Derpy. "Hello-" He suddenly cuts himself off as he rolls his tongue around his mouth. "...New teeth... That's weird..."

"Now where was I? Oh yes! The Third Great Equestrian Empire on one of Galoon's moons!"