Harry Potter/Nightmare Fuel

Books

 * See Harry Potter (novel)/Nightmare Fuel.

The Tales of Beedle the Bard

 * "The Warlock's Hairy Heart". In the liner notes, Dumbledore even points out that many wizard parents won't tell it to their children "until they're in an age where they won't have nightmares".
 * This bears elaborating. A wizard decides he's above the weakness of love, and performs some sort of magic to prevent him from ever loving anyone. He tries to woo a woman to be his trophy wife, but she refuses to marry him unless he shows her that he has a heart.

Films

 * See Harry Potter (film)/Nightmare Fuel.