This is a work of fiction. It is intended to be read like a screenplay. I know it's not the proper format for a screenplay. It's my first attempt at this sort of thing. I welcome your comments. And Mr. Moffit, feel free to use this if you like it.
Interior of the TARDIS
The Doctor, in obvious pain, looks into Clara's eyes.
“Good-bye Clara. See you in a moment”
Regeneration energy engulfs the Doctor. He falls to his knees as the energy wave remakes his body. Clara backs away but keeps her eyes on the Doctor. She sees his features slowly change. Suddenly, it's over. The regeneration energy fades quickly away to reveal the new Doctor. Clara asks:
“Are you alright?”
The Doctor responds:
“Uh...um...I'm not...completely sure...”
The Doctor gets to his feet, but stumbles against the TARDIS console, dislodging a control knob. The Doctor clumsily picks it up and puts it back in place. He looks up at the console and says quietly:
“Sorry Sweetheart”.
He takes a few more uneven steps and says:
?Mirror...I need a mirror!”
He finds a mirror after a few more steps, looks into it and says:
“Oh, Clara! I'm an old man! Blimey! I haven't looked this old in hundreds of years!”
Clara joins the Doctor at the mirror and says:
“It's alright, Doctor. Remember...I've seen all of your faces before. Here...”
She turns the Doctor towards her.
“Let's have a look, shall we?”
She turns his face left and then right. “It's a nice face. You've got a proper chin, now!”
The Doctor looks shocked and turns toward the mirror and says:
“What do you mean? What was wrong with the old one?”
He looks back at Clara who jabs his shoulder and says:
“You know exactly what I mean?”
She smiles and the Doctor turns back to the mirror and says sadly:
“I miss that chin. It was a cool chin.”
Clara says:
“Cheer up, Doctor! You have a new body! With no mileage on it at all! Think of it as...'getting a tune-up' ”.
The Doctor looks at Clara completely confused and says:
“A what?!?”.
Clara answers:
“A tune-up. My dad had a vintage Jaguar that he was oh so proud of. But after each time he got a tune-up, he said it was like getting a brand new car.”
The Doctor looks at Clara and says:
“Seriously, Clara, are you comparing a Timelord to a car?”
Clara smiles and says:
“ It was a very handsome car.”
The Doctor takes another look in the mirror and says:
“Well...still not ginger, and only one more shot at it...”
The Doctor suddenly turns back towards the console, but is staring off into space. Clara looks worried and asks:
“What is it Doctor? Is anything wrong?”.
The Doctor responds:
“Yes...no...yes, I'm not sure...”
The Doctor puts his hand to his head and closes his eyes in thought.
“This is my twelfth life...”
Clara answers:
“Yes, I know.”
The Doctor looks back at Clara and says:
“Timelords are supposed to know when we are near the end of our regenerations. Especially when there is only one left. We don't like to talk about it.”.
Clara says:
“So...it's like a biological clock. What's the problem, then?”
The Doctor answers:
“I don't know how many lives I have left! It could be one or another dozen! I simply don't know!”
Clara looks thoughtful for a moment, then asks:
“Didn't the Council have some control over regenerations?”
The Doctor answers:
“Yes, they did.”.
Clara then says:
“Well, it would seem that since there is no more Gallifrey, there's no more Council to control things. Maybe you will just keep regenerating.”.
The Doctor looks shocked and says:
“Forever? What a miserable existence that would be.”

Interior of the TARDIS
The Doctor, in obvious pain, looks into Clara's eyes.
“Good-bye Clara. See you in a moment”
Regeneration energy engulfs the Doctor. He falls to his knees as the energy wave remakes his body. Clara backs away but keeps her eyes on the Doctor. She sees his features slowly change. Suddenly, it's over. The regeneration energy fades quickly away to reveal the new Doctor. Clara asks:
“Are you alright?”
The Doctor responds:
“Uh...um...I'm not...completely sure...”
The Doctor gets to his feet, but stumbles against the TARDIS console, dislodging a control knob. The Doctor clumsily picks it up and puts it back in place. He looks up at the console and says quietly:
“Sorry Sweetheart”.
He takes a few more uneven steps and says:
?Mirror...I need a mirror!”
He finds a mirror after a few more steps, looks into it and says:
“Oh, Clara! I'm an old man! Blimey! I haven't looked this old in hundreds of years!”
Clara joins the Doctor at the mirror and says:
“It's alright, Doctor. Remember...I've seen all of your faces before. Here...”
She turns the Doctor towards her.
“Let's have a look, shall we?”
She turns his face left and then right. “It's a nice face. You've got a proper chin, now!”
The Doctor looks shocked and turns toward the mirror and says:
“What do you mean? What was wrong with the old one?”
He looks back at Clara who jabs his shoulder and says:
“You know exactly what I mean?”
She smiles and the Doctor turns back to the mirror and says sadly:
“I miss that chin. It was a cool chin.”
Clara says:
“Cheer up, Doctor! You have a new body! With no mileage on it at all! Think of it as...'getting a tune-up' ”.
The Doctor looks at Clara completely confused and says:
“A what?!?”.
Clara answers:
“A tune-up. My dad had a vintage Jaguar that he was oh so proud of. But after each time he got a tune-up, he said it was like getting a brand new car.”
The Doctor looks at Clara and says:
“Seriously, Clara, are you comparing a Timelord to a car?”
Clara smiles and says:
“ It was a very handsome car.”
The Doctor takes another look in the mirror and says:
“Well...still not ginger, and only one more shot at it...”
The Doctor suddenly turns back towards the console, but is staring off into space. Clara looks worried and asks:
“What is it Doctor? Is anything wrong?”.
The Doctor responds:
“Yes...no...yes, I'm not sure...”
The Doctor puts his hand to his head and closes his eyes in thought.
“This is my twelfth life...”
Clara answers:
“Yes, I know.”
The Doctor looks back at Clara and says:
“Timelords are supposed to know when we are near the end of our regenerations. Especially when there is only one left. We don't like to talk about it.”.
Clara says:
“So...it's like a biological clock. What's the problem, then?”
The Doctor answers:
“I don't know how many lives I have left! It could be one or another dozen! I simply don't know!”
Clara looks thoughtful for a moment, then asks:
“Didn't the Council have some control over regenerations?”
The Doctor answers:
“Yes, they did.”.
Clara then says:
“Well, it would seem that since there is no more Gallifrey, there's no more Council to control things. Maybe you will just keep regenerating.”.
The Doctor looks shocked and says:
“Forever? What a miserable existence that would be.”