A little mouse is constantly suffering due to its deep fear for the cat. A wise magician feels mercy for the poor animal and uses his magic to change it into a cat.
Later the cat discovers that it's now afraid of the dog. The magician again uses his power and changes it into a dog.
Then the dog is afraid of the panther and the magician uses the same procedure.
Finally the panther is afraid of the man, but the magician this time changes the animal into a mouse again.
-it's useless- he says- there is nothing I can do for you because you'll always have a mouse's heart.