The swineherd cannot already be wed to the princess when he embarks on his adventures, nor can the boy knock at the witch’s door when she is away on vacation. The wicked uncle cannot be found out and foiled before he does something wicked. Things must happen when it is time for them to happen. Quests may not simply be abandoned; prophecies may not be left to rot like unpicked fruit; unicorns may go unrescued for a long time, but not forever. The happy ending cannot come in the middle of the story.”
