Probably not. 'Knocks up' has a rather suggestive meaning which might not be suitable for younger audiences. Fanfics can range in content, but such a phrase implies mature themes that are not family - friendly.
It could be a story about an accidental magic mishap. Maybe Harry and Marietta are working on a complex spell together in Hogwarts and something goes wrong that causes a false - positive type of pregnancy - like situation, which is really just a magical illusion. Then they have to figure out how to reverse it before the whole school finds out.
I'm not sure specifically as there could be many different interpretations in fanfic. It might be a fictional story where Harry has a relationship with Marietta and she becomes pregnant. However, this goes against the original 'Harry Potter' canon in many ways.
No. The fanfic community generally adheres to certain ethical and moral standards. This kind of content involving underage and inappropriate sexual situations is completely unacceptable.
Finding such a specific fanfic can be quite difficult. You could start by searching on major fanfic websites like Archive of Our Own (AO3) or FanFiction.net. But keep in mind that not all fanfics are easy to locate, especially ones with such a particular plot.
No, it is neither appropriate nor ethical. Fanfic involving such a scenario is highly disturbing as it involves inappropriate and illegal relationships. It goes against basic moral and ethical values, especially when it involves a child in such a situation which is unacceptable in any civilized society.
It can be extremely traumatizing for the readers, especially those who have a sense of right and wrong. It also spreads a very wrong message about relationships and can desensitize people to the seriousness of inappropriate and illegal relationships.
In fanfiction, if such a situation were to occur, it would likely cause a great deal of chaos. Harry and Hermione would have to face the unexpected pregnancy at a young age while also dealing with their duties and the expectations of their friends. Their relationship would be put under extreme stress, and they'd need to figure out how to balance their magical lives with impending parenthood.
This is a very inappropriate and unethical topic. Fanfic should generally be based on positive, legal and ethical content. We should not promote or explore such improper themes.
One common theme is redemption. Since Marietta had the incident with the D.A. list, many fanfictions focus on her redeeming herself with Harry's help. Another theme is friendship. Writers like to explore how they could become friends despite the initial differences.