Note: This story is purely for fun and ignores the entire second half of Series 6, except for Let's Kill Hitler.
"You know, Doctor, the 2050's really ended up being a let-down. I mean… where's all the flying cars and robots and floating cities?"
"Amy, Amy… most of that doesn't happen for a while. More like the 4050's. You really should have specified!"
"And just how was I supposed to know that? Hello?"
"Urgh!" said Amy, and threw her arms into the air in displeasure. "You know what I meant!"
Rory and River Song stood on the sidelines, watching the two argue. The latter had appeared out of nowhere as she usually did to accompany them, and all figured that something extraordinary was going to take place… but all that had happened was a small detour to a newsstand and a small snack of a few bagels.
Everything was about to change.
The TARDIS doors suddenly burst open, and an old woman stood at the entrance. She was very pale and looked as if she would fall over at any moment… which she did, and slammed face-first onto the floor. Having been glancing at the doors for some time, River was the first to notice and ran to the woman's aid. She crouched down beside her and took one of her hands with her own.
"It'll be okay, you'll see." she whispered, and then turned to the Doctor and her parents. "A little help here, if none of you mind?"
River's words snapped the other three back into reality, and the Doctor ran and lifted the woman up with River's help. It took all of a split-second before he realized just who was in the TARDIS, the very instant he saw her face. It may have been more wrinkled with age and her hair dark grey, but there was no mistaking her eyes.
She noticed him staring at her, mouth gaping like a fish, and smiled. "Hello, Spaceman. It's been a while."
The Doctor didn't need to ask who this woman was. No, he knew… and also realized that she had very little time left. As he laid both of his hands upon her face, he could literally feel her mind beginning to burn. There was no stopping it.
Donna Temple-Noble was going to die.
She looked at the other woman near her. "Hey, River. I suppose you haven't met me, but I've met you before."
"River, this is not a time to joke!" said the Doctor. "My best friend is about to burn up and all you can say is spoilers? And Donna, don't say anything more to River… you know what I'm talking about."
"Oh, this is going to be wonderful!" said River, and she rubbed her hands together. "Doctor, trust me when I say she's going to be fine."
Donna didn't know what River was rambling on about, and frankly she didn't care. Months ago, she had been diagnosed with inoperable brain cancer, which had the interesting side-effect of allowing her to remember the Doctor without suffering a painful, horrifying death. For many weeks she had taken it upon herself to find the Doctor one last time, but it seemed as if she was too late. She no longer had the strength to stand, and as she tried to speak she realized that function was also gone. The Meta-crisis was about to overcome the cancer, which would have been fine if it didn't have the unfortunate side-effect of death.
"What's happening? And who is she?"
"There's no time for that right now, Amy!" said River. "Donna, look at me. You might not be a complete Time Lord, but your body is yearning for something. You know what it is, and you have to do it! Focus on it with everything you have left, Donna! Fight! Doctor, get us into the Vortex immediately! There's no time to lose if this is going to work!"
He did so, and mere moments later Donna miraculously found the strength to lift herself on her two feet. River was still next to her, now standing, but looking at the older woman with wonder and awe. Donna was grinning and looked about ready to burst into laughter. Poor Rory had been lost ever since the TARDIS doors opened, and didn't know what to make of anything that was taking place.
"I understand. I can feel it, just ready to come out… and I can feel the TARDIS reaching into me. Let's just hope this works!"
A faint golden glow, which the Doctor and the others recognized as the beginning of regeneration, began to flow around her. River ran and stood by the Doctor, and urged everyone to stand back.
"If you thought Berlin was something, wait until you see this!" she said.
Donna screamed as the regeneration energy exploded from her arms and head. The Doctor stared at the display in complete shock and fascination. If anyone could do the impossible, it was Donna. She was his biggest regret and his biggest failure, and many times he had been taunted in his nightmares by her, accusing him of not doing enough.
And now she was standing not ten feet away, regenerating.
As soon as it was over, the first word that came to the Doctor's lips was one that his previous regeneration was quite fond of using.
Looking back at him was none other than River Song.
"Well, it must have worked, since I'm not dead. Wait… my voice! Why do I sound like… like River?" she said, and noticed blonde curls dangling. She reached and twisted one with her right index finger. "Oh."
"But, but…" said the Doctor. He didn't know if those words were an improvement, but at that time he was unable to form coherent sentences.
Rory took over, and spoke up for the first time since everything started.
"How can you be River? I mean, she was Mels and then regenerated into River, and then you do too?"
"I'm sorry, but I don't know who you are, or the redhead next to you. I don't know what's happened, to be perfectly honest. But you do, don't you River! I mean, I'm happy to be alive and all but that doesn't explain how I was able to regenerate, or why I'm now a clone of you!"
"Yes, I would like to hear this as well, River." said the Doctor. He had recovered for the moment. "This shouldn't have even been possible! No offense, Donna. Or River. Or Donna-River. Maybe River-Donna?"
The Doctor had always longed to hear those words again, but they sounded quite different with River's voice and accent. He still couldn't believe it. Donna was back! In a different body, yes, but back! In an uncharacteristic move even for him, he ran and hugged her as tight as he could, and couldn't stop the flow of tears any longer.
"Donna, I'm so sorry! For everything! I really shouldn't-"
"Hush." she said, silencing his lips with a finger. "I forgive you, Doctor. Now, everyone, I think there is quite a lot that needs to be discussed. Doctor, who are these people? I know you and River, but…"
"Ah, I'd nearly forgotten they were here! Donna, meet Mr. and Mrs. Pond, Rory and Amy. You know, I never took on a full-time companion after you until I crashed the TARDIS near little Amelia's house."
"Yeah, and you left me waiting for twelve years!" said Amy.
"Yes, yes… and Rory is her husband, and River is their daughter. Don't ask her anything about your future, even though she obviously knows, because she'll just say-"
"Spoilers!" said Donna, in a perfect imitation. "Wow, I'm good."
River laughed and put an arm around her twin's shoulders. Except for the clothing, both women looked completely identical in every possible way.
"You know, I've always wanted a twin sister."
"What?" said Donna.
"I didn't just come here today for a jolly old stroll. No, I knew this was going to happen. Donna, the only reason you were able to regenerate was that you were inside the TARDIS itself, and near me, or else you would have died. The Vortex supplied enough energy to make it work, and since I'm the only female Time Lord around to be used as a template…"
"Wait, you're a Time Lord?"
"Partially, though that is quite a long story to tell."
"Basically," said the Doctor, "Amy and Rory here cooked up a Time Lord on their wedding night, in the TARDIS. And by cooked up… well…"
"Gee, thanks Doctor!" said Amy. Rory wrapped an arm around his wife and chuckled, and she playfully hit him in response.
"So what happens now?" said Donna. "What am I going to do? I'm River Song now! I don't know anything about archaeology! And almost everything I knew as the DoctorDonna is gone! Oh sorry, spoilers… I think? No offense, River."
"None taken! And you'll learn everything you need to know. This is the earliest I've ever seen you! Oh, and except in private in some cases, you can't call yourself Donna anymore. Not now."
"River, of course! We're both River Song! And so, Doctor, today you've learned another one of my biggest secrets. One of our biggest secrets!" She said, rubbing the other River's hair hard.
"Ow! Technically, I'm older than you, little sister!"
"So let me get this straight," said Rory, "my daughter has a twin that's not really her twin, and in a way I have another daughter now?"
"Sort of, dad." said River. The other River looked perplexed and a bit dizzy, and River then spoke to her. "I know this is a lot to take in all of a sudden. You look tired, and regeneration doesn't always work the same way every time, so you'll need to sleep for a while."
"Is my old room still here?"
The Doctor nodded, and she wasted no time in leaving the console room to have a well-deserved and needed rest. River's revelation of one of her biggest secrets was going through his head like a hurricane… they're both River Song. Spoilers be damned, he was going to ask her the question that he probably already knew the answer to, but he needed to be sure.
"River, when you say that you're both River Song, does it mean that… that you switch out, so to speak? That there's no way of telling which is which?"
"Oh, there are definitely ways of telling, but what is the fun in that? Spoilers, you know. The only two times that I'll say were definitely me were at Demon's Run and most obviously in Berlin. Doctor, this is also a second chance for her. She's always wanted to be back with you, even subconsciously, for most of her life. In many ways she is just like me, and I'm not saying that just because she looks like me either. It's all beginning for her right now, and in time we're going to be best friends and do great and terrible things and run."
The Doctor considered everything that had taken place in the space of half an hour. Every single time he thought that the universe couldn't surprise him, it did, and often in the worst possible way. But, this was something unprecedented by all possible standards.
Now he had two mysterious women instead of one, to both annoy and love him. If Rose came back and also somehow turned into River Song, he just knew that his head would explode into gibs, and indeed it was paining at the mere thought.
He had a sudden craving for fish fingers and custard, and quite possibly banana pudding.
Many years later…
"You can't let her do this, Doctor!"
"It's her decision, River. And you know her, once she sets her mind on something there's absolutely no stopping her. I've already said goodbye and given her the sonic screwdriver, and she's meeting with Strackman Lux and his party as we speak… I'm so sorry, River. It was so hard for me to let her go."
"It's just not fair! She shouldn't have to die!"
"No, it's not fair." said the Doctor, and held River in his arms. He always knew that this day would come, but had never expected the other River to take her place in the Library. Over the past year, he noticed that she seemed to be growing steadily weaker, and his suspicions were confirmed when he scanned her in the TARDIS.
While the regeneration had succeeded and given her new life, it wasn't without flaws. The Meta-crisis hadn't been destroyed or absorbed by the regeneration as everyone thought, but was quite deeply buried within her mind… and it was leaking out. There was no stopping it, and the same trick River pulled once before wouldn't work a second time.
She was dying, again.
The River Song who was once known as Donna Temple-Noble remained his best friend for the rest of her life, while her sister was his lover. She didn't mind at all, and fully supported their relationship, once saying:
"Well, I don't blame you if you don't want to share, but how can you stand his forehead? And he's even more alien than my old Spaceman!"
"Hey! It's not like you can pick and choose your regenerations like clothing!" said The Doctor. "And I do happen to actually like this forehead!"
"Oh, I know that, sweetie. And I am quite fond of this hair… did you know I got tired of ginger a few years after I was married? Let's just say that Shaun and granddad got to know what a bad hair day truly means!"
"How could you get tired of ginger? I've always wanted to be ginger!"
"I also used to be ginger, long ago," said River, "but I was spending too much time being brainwashed to really care much."
"You too? That's it, the universe is officially against me!"
Both Rivers Song laughed heartily at the Doctor's misfortune, to the point where the Doctor left the console room briefly and came back wearing a red clown wig, which only made them laugh even harder. Soon, the Doctor himself joined in.
Memories such as those were cherished and remembered for all they were worth, because nothing lasts forever.
Having lived it through it long ago, she knew that River's time was soon to be up, but what if there was a way around it? Death could be cheated if you knew how.
So she told River the one thing that the Doctor ordered her to never tell, that she had once been to the Library and met River Song, who then sacrificed herself to save everyone. The Doctor knew, long before she was even born, how and when and where and why she was supposed to die.
Despite her own stance on spoilers, she was furious at them keeping such a terrible secret, but horrified at the burden they must have carried for many years.
And so, many arguments about fixed events and spoilers later, the woman who bore her image and identity was gone, never to return.
The Doctor and River went to the Library, while the day of amnesty was still in effect, to retrieve the diary left behind. It was the only one, shared by both sisters with two very different handwriting styles. River's own was clear, clean and elegant, while the other's was rather crude at times but steadily improved over the years.
On the last non-empty page, a short message was written directly to her.
If you're reading this, then I am dead. My time should have came a long time ago, but you saved me and gave me a second chance. Now I'm doing the same for you. Both you and the Doctor deserve much more time together. Take care of him.
I love you both.
"I will, Donna. And I love you too, big sister." Said River, and could no longer contain her grief as she cried into the Doctor's shoulder.