In the tale, a spoiled princess reluctantly befriends the Frog Prince (meeting him after dropping a gold ball into a pond), who magically transforms into a handsome prince. Although in modern versions the transformation is invariably triggered by the princess kissing the frog, in the original Grimm version of the story the frog's spell was broken when the princess threw it against a wall in disgust.[1]
In other early versions it was sufficient for the frog to spend the night on the princess's pillow.
A Russian folk version "Tsarevna Lyagushka" (The Frog Princess) has the male and female roles reversed: the male prince Ivan Tsarevich discovers the enchanted female frog who becomes Vasilisa the Wise, a female sorceress.