In George MacDonald's The Princess and Curdie, Curdie is informed that many human beings, by their acts, are slowly turning into beasts; he is given the power to detect the transformation before it is visible, and is assisted by beasts that had been transformed and are working their way back to humanity.
In C. S. Lewis' The Chronicles of Narnia, Eustace Scrubb transforms into a dragon, and the war-monger Rabadash into a donkey. Eustace's transformation is not strictly a punishment - his transformation simply revealing the truth of his human nature. It is reversed after he repents and his moral nature changes. Rabadash is allowed to reverse his transformation, providing he does so in a public place, so that his former followers will know that he had been a donkey. He is warned that, if he ever leaves his capital city again, he will become a donkey permanently, and this prevents him leading further military campaigns.
Also in The Chronicles of Narnia the Dufflepuds are dwarfs who have been transformed into monopods as a punishment. However, it ultimately transpires that they are happier with their new form.
In the novel I, Coriander by Sally Gardner, Prince Tycho is transformed into a fox after refusing to marry Undwin, Queen Rosmore's daughter.
Some giants abducted humans to reduce them to slavery. In the famous Irish legend of Prince Diarmuid, the giant of the forest of Black Beech was holding captive three women. For a given to maintain its appearance, but the other two, turned for fun in a dog and a horse.
In The Marmot Queen by Italo Calvino, a Spanish queen is turned into a rodent by the Morgan le Fay.
In a Turin Italian tale by Guido Cozzano: The Mare of the Necromancer, the Princess of Corelandia was turned into a horse by the baron necromancer for refusing to marry him. Only love and intelligence of a nice guy named Candido save the princess from the spell.
The Neapolitan tale written by Giambattista Basile: The Deer in The Wood describes the transformation of Princess Desiderata into a doe. Envy and jealousy of a fairy who saw his unrequited love, because of the beauty of the noble lady, she decided to take revenge on changing it into a deer. Here, too, will always be the prince to save his beloved princess from the evil spell.
Photo: The Sartorialist