Talking animals are often the hero's helpers, perhaps more than any other type. The most common motivation of the animals is gratitude, after protection, receiving food, or (less commonly) settling a quarrel between several animals. In another variation, featured in "The Three Enchanted Princes" and "The Death of Koschei the Deathless", the hero's three sisters have been married to animals. These prove to be shape-shifted men, who aid their brother-in-law in a variant of tale types. Because of its retelling by Perrault, "Puss in Boots" is among the best known animal helpers, although in other variants of the tale, the hero (or heroine) is helped sometimes by a fox and occasionally by other animals. Horses, as in "The Firebird and Princess Vasilisa", "Făt-Frumos with the Golden Hair", "The Magician's Horse", "The Princess on the Glass Hill", and "Ferdinand the Faithful and Ferdinand the Unfaithful", are popular in the oral tradition; several tale types normally feature a horse almost as important as the hero.