Rump by Liesl Shurtliff. Relates the tale of Rumpelstiltskin's childhood and youth, explaining why his name is so important, how he is able to spin straw into gold, and why a first-born child is his reward for helping the miller's daughter-turned-queen.
Every word problem back in elementary school. I've also had derpy teachers who have accidentally made impossible word problems. so we would freak out thinking we didn't study enough to find out our teacher apparently needs to go back to school.