Perhaps it involves a scientific experiment. A scientist was working on some gender - related gene - altering experiment. There was an unexpected reaction in the lab, and the subject was violently transformed into a woman. This might also lead to a story about the person's struggle to adapt to the new physical and social aspects of being a woman.
It could be an ordinary man. Just an average guy going about his day until this strange and violent transformation happens to him.
One possible plot could be a magical or scientific experiment gone wrong. Maybe a white man enters a strange laboratory and an accident occurs during an experiment on genetic transformation, turning him into a black woman.
Magic or supernatural powers could be another reason. Maybe there is a magical object that, when misused by a man, causes this transformation. It could also be part of a grand design by some higher - power entity in the story's universe to teach the man or society a valuable lesson about gender and pregnancy.
One possible plot could be that a woman is exploring a jungle and accidentally stumbles upon an anaconda's territory. The anaconda, being a predator, sees the woman as a potential threat or prey and starts to approach her. The woman then has to use her wits and any available resources to escape from the anaconda.
Magic is a big reason. As mentioned before, an evil spell from a witch or wizard can cause the transformation. It could be out of spite or as part of a more complex magical plot.
Well, perhaps it could be a magical tale where a witch curses a woman and she turns into a horse. Maybe she has to go on a journey in her horse form to find a way to break the curse.
One possible plot could be that a woman rescues a dog. As she takes care of the dog, they form an unbreakable bond. The dog becomes very protective of her and through their adventures together, they face challenges in the community. Maybe some people don't understand their relationship at first, but eventually they see how much the dog and the woman mean to each other.
Perhaps it's a magical or spiritual journey. The woman enters a strange realm where she has to transform into a worm to learn some important life lessons. She then has to figure out how to transform back to her human form while facing various challenges in the worm - like state.
Maybe the woman found the python in the wild and decided to take it home as a pet. Then she had to learn how to take care of it, like feeding it proper food and providing a suitable living environment.
Well, in such a story, it could be that the woman was on an expedition. Then she accidentally entered the territory of the natives. They captured her perhaps because they saw her as an intruder. She would then have to find a way to communicate with them to gain her freedom, or wait for her fellow expedition members to rescue her.