Not all fish that swim

Once upon a time there was a place where my brother and I were normal kids. The next moment, a mirror sniffed us and flew us into the world of fairy tales. We didn't want to confuse either Snow White or Cinderella! It was all a matter of chance. But the fate of the little mermaid is very sad. And the magic mirror just dropped us right in front of his fins. We need to find a happy ending to the tale before the little mermaid becomes fish food, and we take her to the sea forever.