Alyonushka and her naughty brother Ivanushka.

«Ivanushka says:

- Sister Alyonushka, I can’t stand it: I’ll drink from a hoof!
- Don't drink, brother, you will become a goatling!

Ivanushka disobeyed and drank from a goat's hoof.
Drank and became a goatling ...»

@Russian folk tale