9. The Girl in the Fireplace
I know there's a Series Six episode called The Girl Who Waited, but Reinette, the 18th Century Frenchwoman will always be the girl who waited to me. Reinette first meets the Tenth Doctor as a child when the Doctor and companions investigate an abandoned spaceship. The Doctor steps away from Reinette seconds for what seems like only seconds, but he returns to find her now months older. He is forced to take leave of her again to protect her from the clown-android living under her bed. When he returns a second time, he's surprised but pleased to find Reinette now looks strikingly similar to Sophia Myles. Reinette is now Madame de Pompadour, the mistress of King Louis XV, a man who took the throne at age of five and became famous for... well, I'm not a scholar but I think his greatest achievement was Madame de Pompadour. Of course in the Doctor Who universe, things go awry as the mandroids try to use Reinette's brainpower to re-power their ship. The Doctor saves Reinette by horseback and leaves, promising to return. When he arrives for his final visit with Reinette, he learns she had passed away many years prior. He pockets a letter she wrote him, where she states that against all reason she believes her lonely angel will visit her once more before passing. (Spoilers: he doesn't).