Martha Jones:  Thing is , though , am I missing something here ? The world did n't end in _ 1599 _ . It just did n't . Look at me , I 'm living proof .
The Doctor: Oh , how to explain the mechanics of the infinite temporal flux . I know : Back to the Future . It 's like Back to the Future .
Martha Jones: The film ?
The Doctor: No , the novelisation ! Yes , the film ! Marty McFly goes back and changes history .
Martha Jones: And he starts fading away- Oh my God , am I gon na fade ?
The Doctor: You and the entire future of the human race . It ends right now in 1599 if we do n't stop it .