Rose: Think about it, though. Christmas 1860. It happened once. Just once, and it’s… gone, it’s finished. It’ll never happen again. Except for you. You can go back and see days that are dead and gone, a hundred thousand sunsets ago. No wonder you never stay still.
The Doctor: Not a bad life.
Rose: Better with two.Doctor Who Episode Posters 1.03 - The Unquiet Dead
