Story
The creek of the TARDIS doors opening is the most common sound Twilight loves to hear, it's a close second to when the TARDIS actually materializes.
"So? Equestria is safe once again Doctor, you did fantastic out there." Twilight praised with a smile.
"Heh, I guess I should feel great after today. It was..." He paused, softly frowning as he leaned against the TARDIS's controls and pulling a lever down. "Most interesting."
Twilight never noticed the frown because she was to distracted by her beaming smile, she couldn't wait for the next adventure. "Where to next Doctor?" She asked in a calming tone.
The Doctor looked down. "I'm going to miss that smile." He mumbled.
Twilight raised an eyebrow. "What was that?"
"Nothing! I was thinking more of the lines of going to the Islands of Goberstrate. I've heard they have a plant that eats candy-AGH!" The Doctor collapsed onto the ground and shivered. Twilight gasped in surprise and knelt down to him.
"Doctor? What happened are you alri..." She cut herself off when she noticed a golden glow come from his hooves. "No... Doctor," She backed up. "You told me about this before..."
The Doctor shut his eyes, not wanting this to go through. He didn't want to change, there was still so much for them to do. He didn't want to die and have some other take his place. "I... Can't..." He grunted.
Twilight started to get both sad and irritated. "What did this to you?!" She cried.
The Doctor got back up and turned to his faithful companion. "The time we got separated... I set myself to find you, I..." He grunted more, breathing heavily. "I got ambushed..." The Doctor took off his blue suit jacket and dropped it on the floor. He revealed what had got him, a burn mark on the front of his chest.
Edit: Music
Twilight covered her mouth as tears began to fall. "Why didn't you tell me?" Her voice cracked.
He chuckled. "Because then you would worry... You would always worry... That's what made you perfect..." He put a hoof on her cheek as he softly smiled as the golden glow began to come out of his body and began tracing over the Doctor's head. "The first time we met I've told you what happens when I regenerate, you know what must happen." He shut his eyes and pain shot through him once again. "I want you to remember what I told you, when you were grabbed by the Weeping Angels."
"Pegasus." Twilight corrected, continuing to cry..
The Doctor chuckled. "Come on, you already gave me enough when I kept getting your name wrong." He took a deep breath. "Just remember these words. 'I need you to be brave for me Ms. Sparkle...'" The Doctor jolted back as the golden glow became more thick.
"Doctor!" Twilight cried once more as tears continued to show themselves.
The Doctor leaned down with his rump still in the air as he continued to breath heavily, his eyes opened and a smile creased his lips as he looked up at the first equine he had ever met in this universe. "I've saved you countless of times Twilight... Now I need you to save me." The glow grew thicker and thicker as the Doctor pushed himself back to his feet slowly and looked into the air.
"Doctor..." Twilight whimpered.
The Doctor locked eyes with Twilight and smiled at her one last time before closing his eyes and shutting his mouth.
The golden glow of Time Energy blew it's fuse as the entire glow covered his entire body and his red tie was ripped off by it, The glow began shifting as the glow suddenly disappeared. The Doctor jolted back and shook his head violently, a headache occurring within his Time Lord mind.
Twilight stared at the stallion in front of her, not even remotely recognizing him but she knew who he was. "D-Doctor?" She stuttered, tears still flowing.
The Doctor looked up at the lavender mare with a shocked expression, his new look of a darker shade of grey and black hair. His eye color was light grey, he seemed to be lacking color on his new body but it made up for when a large smile was planted on the stallions lips. "Twilight! It's good to see a friendly face." He then noticed the shocked expression on her face. "What is it, is something behind me?" He asked as he turned around, he then began looking at his body. "Is there something on me? Or around me? OR! Is it because I'm-" He looked at his tail and groaned. "Not ginger!" He then began checking his forehead. "Not even a unicorn nor Pegasus, ugh! Looks like I'll have to wait for the next regeneration."
Twilight continued to stare, she sat down on her haunches and suddenly looked down. She couldn't find any words to say or think of anything for that matter. She then felt a hoof on her shoulder and looked up at the mysterious stallion above her only to see a smile on his face.
The TARDIS then shook with a vigorous rage that snapped the Doctor back into reality. "Oh no." He quickly moved around the controls, pressing and pulling. "No no no no no!" He panicked.
Twilight decided to ask about things later and held onto the nearest thing next to her. "What's happening?!" She shouted.
"The TARDIS is being dormant, it won't listen to me! It's taking us somewhere and I have no idea where!" He then grabbed the monitor and his eyes went wide at what he saw. "Okay, Good news or bad news?" He asked as he turned to Twilight.
"What's the good news?" Twilight asked as she continued to hang on.
The Doctor smiled. "Good news is we're going home!" He chuckled as he then started to frown. "Bad news..." He paused. "We're crashing."
Twilight groaned. "You've got to be kidding me!"
The Doctor started laughing once more, his serious attitude seemed to have faded from his last body as this one liked the sense of danger. "Oh yes! New body, new brain, new. EVERYTHING!" The Doctor shouted. "And do you know what that means Sparkle?" He asked.
Twilight looked at the Doctor. "What?"
The Doctor grabbed onto the rail next to her and smiled brightly. "New catchphrase!" His laughter seemed to have calmed Twilight a bit but still holding on for dear life as the Doctor's new phrase rang through her ears.
"COWABUNGA!"