Folklore is full of stories of enchanted animals - some have magical powers, and some are trapped in their animal form until released by some act of bravery. In this instance, we focus on a compilation version of a princess trapped in the form of a frog. This is only one of many variations. If you are curious, you can check out these links for royalty in frog form:
https://en.wikipedia.org/wiki/The_Frog_Prince
https://en.wikipedia.org/wiki/The_Frog_Princess
The king wants his three sons to marry. To accomplish this, he creates a test to help them find brides. The king tells each prince to shoot an arrow. According to the King's rules, each prince will find his bride where the arrow lands. The older two sons' arrows land in the houses of daughters of an aristocrat and wealthy merchant, but it turns out the daughters are rather lazy and spoiled. 
The youngest son Prince Ivan's arrow is picked up by a frog in a swamp. The king assigns his three prospective daughters-in-law various tasks, such as spinning cloth and baking bread. In every task, the frog far outperforms the two other lazy brides-to-be. The frog uses magic to accomplish the tasks, and though the other brides attempt to emulate the frog, they cannot perform the magic. The frog princess, previously known as Vasilisa the Wise, had been a beautiful, intelligent, friendly, skilled girl who was forced to spend 3 years in a frog's skin for disobeying the terrible Koschei. Still, the young prince Ivan is foolishly ashamed of his frog bride until her true identity as an enchanted princess is finally revealed in the transformation back into human form.
Illustration to
The Frog Tsarevna by Ivan Bilibin
Vasilisa the Wise waits in hiding for the right one to come along ... Someone who can see through her disguise and recognize her true identity. Will you be the one? Please be gentle!