(Colin and Dennis Creevey's mother reads to them stories from the big Hans Christian Andersen book she owns every night when they are young, and in the way that the things in early childhood always stick with you, those tales remain ingrained in Dennis's head for the rest of his life. Eventually they run out, so she starts over again, accidentally repeating The Sandman a little too much.)
And so when Dennis looks at the small, delicate bodies of the dead Hogwarts students who snuck back in to fight and the seventh years who fought as well—students that, if not the for the staring eyes on most, look like sleeping kids—he wonders what would have happened if only the Sandman hadn't sprinkled too much sand in their eyes, hadn't surpassed dreams and crossed into death.
The answer doesn't even need to be thought: Colin, alive, eyes sparkling. All the other students, alive, with the long lives ahead of them they should still have.
This was not the right time for the Sandman to make a mistake.
Colin's eyes are closed, and his face bears no sign of the fear he must have felt in the moments of his death. He is peaceful and looks even younger than he did alive, like a boy and not a seventeen-year-old.
"Sandman," Dennis murmurs, blinking furiously (he hasn't gotten to the stage yet where he realizes it's no use not crying), "what have you done?"
(Chosen the side of a man called Lord Voldemort.)
Ridiculously short, meh-ish prose...but I like the idea, so it's up here.