The Rape Theory is a theory about Kraina Grzybow originating from the Mushroom Melody. It states that Agatha was raped by the Jeansman, a pedophile.

From a Polish comment on the original Mushroom Melody:

"This is what I have written before, but no one thought it fitted the video. 
Agatka was called a cow in her childhood - other children mocked her, probably because of her body type (fat cow, krówsko) - Agatka's mother says that her daughter complaied that other children made fun of her, she was a class victim. "Do you want to be a wallflower or have a great time?" (...) A class victim is obviously not the most sociable person, when going to a "school disco", she stands / sits and does nothing ("wallflower"), and someone would come, call her "wallflower" and suggest she joined the dance. It is possible that she agreed, hence her "dance", bulb-screwing hand motion. This person could be a teacher or a senior colleague who later raped her. Agatka then ran away from home or committed suicide - went to the Land of Mushrooms, which is easy to hit, only the back is a little bit worse. 
Apple drilled through, knife, very painful looking "treatment", a theme of painful deflowering (shown many times very clearly). A drawing of a cow with the word "Mama" - was called a cow, then she became a mother. Many things might tell us about the death of Agatka (even "you're full of mushrooms" or calling her the Snow Queen - cold body). Numerous things telling us about Agatka's pregnancy (eg. scheme: apples - egg, a drawing of a cow's reproductive system, the way of the fertilized egg to the uterus) 

Jeans man was a pedophile who raped Agatka."