Stories are important. People think that stories are shaped by people. In fact, it's the other way round. Stories... have evolved... The strongest have survived, and they have grown fat... Stories etch grooves deep enough for people to follow... A thousand wolves have eaten grandmother, a thousand princesses have been kissed... Stories don't care who takes part in them. All that matters is that the story gets told, that the story repeats.
And once again, Probability proves itself willing to sneak into a back alley and service Drama as would a copper-piece harlot.
— Vaarsuvius, The Order of the Stick
Why? Because the plot says so!
Thing: Reed - you spoke of transmutations. Can you restore to me my humanity? I have been a monster for too long.
Richard Reed: In truth, I do not know, my friend. The natural sciences say yes, a cure is possible. But the laws of story suggest that no cure can last for very long, Benjamin. For in the end, alas, you are so much more interesting and satisfying as you are.
Because I lost. Because as the villain of a children's story, that is all that I can do.
House: So... what "Force" is protecting him? If you start quoting Lucas, I'm going to get the idiot in the cowboy hat to shoot you. A lot.
The Tenth Doctor: Oh, that? No, it's far greater than even a science-fiction thingamabob.
The Tenth Doctor: It's Narrative Convenience.
Jareth: What are you doing here?
Javert: Good question. Why are we always loitering here, James?
James: I dunno. 'Coz Erik has the biggest TV set?
Jareth: Narrative Convenience.
James: Or that. ... Beer?