The Legend of the Wickedelfchild

Ok, so it's not so much a legend as a childhood story.

Once upon a time, there was a little girl named Anne Marie, who was the most beautiful little girl in the kingdom, with curly dark hair and a smile that could light up the world. Anne Marie was not only beautiful, but she was good. She always ate her vegetables without complaining. She always cleaned up her room. She never forgot to say, "please," and, "thank you." She helped her mother around the house. She was kind to animals. Everyone who met her, whether they had two legs or four, immediately fell in love with her.
Now it happened that in the kingdom there also lived a beautiful elf queen who had a wicked little elf child. The wicked little elf child was almost as beautiful as Anne Marie, but the wicked little elf child was not good. She was wicked. She never ate vegetables. She ate only cake and candy. And chips, she also ate chips. Whenever she did not get her own way she would sit down on the floor and kick and scream. She would hit anyone who came close to her.
The beautiful elf queen did not know what to do. She began to despair of what would happen to her beautiful but wicked little elf child. One day, the beautiful elf queen’s envious eyes fell upon the beautiful and good Anne Marie. And the elf queen was filled with covetousness, with envy for the mother of this beautiful and good little girl and so she made a plan.
In the middle of the night, she snuck into Anne Marie’s house and she exchanged her beautiful but wicked elf child for the beautiful but good Anne Marie. In the morning, when Anne Marie’s family woke up, Anne Marie was still beautiful, but no longer good. She refused to eat her oatmeal. In fact, she picked it up and threw it at her mother. When told she could not have Pop Tarts for breakfast she sat down on the floor, kicked her feet and screamed.
Meanwhile the beautiful elf queen lived happily ever after with the beautiful and good Anne Marie. 

This story was told to me by my aunt. As I recall, I've been hearing it since I was three or so. For the record, Janie swears she didn't tell it to me until my early teen years. Also for the record, she's mistaken.