1.
She runs away to Romania when she turns eighteen, no use staying where she knows she doesn't belong. She is nothing in comparison to her siblings, parents, aunts, uncles, cousins, and grandparents, she doesn't have any magic at all, but she does have something. Lily Luna Potter has a dream, and there is no way that dream can come true anymore, because she isn't special; she stopped believing in magic a long time ago.
So when a man in suspenders and tweed literally runs into her, sending them both toppling to the ground she thinks, 'what the hell?' and follows him into his strange blue box that is much bigger on the inside than out and suddenly she thinks that her dream really might come true.
2.
It's spectacular at all times, saving the world. They explore new planets and rescue new creatures on a daily basis but, sometimes, Lily Luna just prefers to just sit around with her best friend. After they have just saved the universe for what seems like the hundredth time it is always so relaxing for her to change into her silk pajamas as the Doctor steers the TARDIS into the Vortex. They hang out in the galley and talk about places they have been and things they want to see while they play dumb games like Yatzee or Kings in the Corner.
It may not be the most impressive sounding part of her life with the Doctor, but to Lily Luna, it's definitely her favorite.
3.
Sometimes, when the Doctor is getting on her last nerve, Lily likes to go out and kick some monster ass. She doesn't know how she survived living with a family of wizards who were always teasing her about her lack of abilities without going psycho killer on them. She needs the aliens, the monsters, to help calm her down, and the running…don't get her started on the running. She can't help but love the running more than life itself.
She'll never ever give this up. Not the Doctor; not the monsters.
While the Doctor is worth the monsters, the monsters are also worth the Doctor.
4.
They are there to see the Big Bang and that is when he asks her if she regrets it, leaving her family and flying off with him. She tells him that she was nothing compared to her relatives, they were all so special and she was not. The Doctor just shakes his head at her and smiles sadly. He asks her what it is with brilliant, pretty girls like her thinking they were nothing.
5.
Sometimes, Lily Luna falls asleep in the galley with a cup of tea set in front of her. To her surprise she awakes in her bed dressed in her silk pajamas. When she goes out to the console room to ask the Doctor if he knows anything about this strange occurrence, she sees that he is under the TARDIS console tinkering with the controls. Instead of interrupting him, Lily just watches the Doctor consumed in his work, and she is somewhat surprised to feel a tingle of electricity run through her body when he finally turns to her and gives her his brilliant smile.
6.
"How long will you stay with me?"
"Forever"
"Really?"
"Of course"
"I just…there was once another girl who told me she would stay…forever…and she was taken from me"
"I promise, I will never be taken from you"
7.
Three years have passed for her when she finally walks through that door, Doctor in toe. Three years of joy, excitement, adventure, fear, and an awful lot of running. Three years that she will never ever dream of taking back. But, when she sees her parents' faces, she knows that she is late.
Her mother pours her tea, her skeletal hands shaking as she does, and her father questions the Doctor about his profession and how much income he brings in each year. Lily is grateful that they don't ask her where she has been or why she is so young after twenty years. Those questions would be too hard to answer. But, her other relatives are not so polite.
Lily finally makes a dash for the door, yells goodbye, and is back inside the TARDIS before anyone can stop her.
"I'm sorry," Says the Doctor
"I know."
8.
She is in the middle of a dream when he awakes her with his cold touch. She feigns sleep, wondering what he is going to do. She hears the rustle of clothes and suddenly he is lying beside her, holding her. His jacket and shirt are gone and she can feel the melodic double beat of his hearts as it lulls her back to sleep.
When she wakes up, he is gone.
9.
They first kiss after she saves him from being eaten alive by a giant squid. When they break apart he asks her how she knew how to defeat the giant squid and she just tells him that, even though this was the first time she had ever seen this kind of monster, her brothers and cousins had told her multiple ways to incapacitate the creatures during summer holidays.
They act as if nothing had happened as they run, hand-in-hand, back to the blue box they call home.
10.
She asks him to take her back home after they battle the Daleks. She moves back in with her now elderly parents and asks for their forgiveness. The Doctor leaves her with tears in his eyes and a false smile plastered across his face.
He feels like dying when she says for him not to come back for her this time. And, secretly, she does too. It doesn't matter how old she gets, she will always need the Doctor.
11.
Five years pass and Lily wants nothing more than to be back exploring the galaxy with her mad man inside his stupid blue box. So, when she hears that familiar noise, nothing can stop her from running down into the living area to find that the TARDIS has parked itself just in front of the fireplace. Lily doesn't look back as she runs into the box and closes the door behind her.
Because, it's always been him, the man who makes her believe in magic.