Everybody knows The Princess and The Frog story, but you may not be aware that it was originally based on a German fairy tale collected in 1812 by The Brothers Grimm called The Frog King (Der Froschkönig).
In the popular version of the tale, a princess is playing with a golden ball when she accidentally drops it down a well. A frog pops up and volunteers to get it back for her, but only if she will be his grilfriend. The princess agrees, but as soon as she gets the golden ball, she forgets all about the frog and goes home. The next day, the frog turns up on her doorstep, demanding to be let in. Eventually, she lets him sleep in her bed and when she wakes up the next morning, he has transformed into a handsome prince.
In the original version, the princess gets so fed up with the frog that she picks him up and hurls him against a wall.
She picked up the frog with two fingers, carried him to her room, and climbed into bed, but instead of laying him next to herself, she threw him bang! against the wall. “Now you will leave me in peace, you ugly frog!”
In a Scottish version called “The Queen Who Sought a Drink from a Certain Well” (1860), the girl chops off the frog’s head with a sword and this is what transforms him into a handsome prince.
…he said to her, “There is an old rusted [sword] behind thy bed, with which thou hadst better take off my head than be holding me longer in torture. She took the [sword] and cut the head off him. When the steel touched him, he grew a handsome youth; and he gave many thanks to the young wife, who had been the means of putting off him the spells under which he had endured for a long time.