I don't think it's a common theme. The Hogwarts Express is often a setting for stories about students going to Hogwarts, their first encounters, and the start of their magical adventures. While there may be some outlier fanfictions that explore other themes, the idea of 'lemon' (if we're talking about adult - like content) being dominant seems very uncharacteristic of the general body of Hogwarts Express fanfiction.
Well, 'lemon' in fanfiction often refers to a type of romantic or sexual content (though it's not appropriate in all contexts). In this case, if it's 'dominated' on Hogwarts Express fanfiction, it might mean that this kind of content is prevalent in those fanfictions set on the Hogwarts Express. But it could also be some sort of citrus - themed or yellow - colored dominance in a more innocent sense if the author is using 'lemon' in a non - traditional way.
One reason could be that he was under a dark spell cast by a new enemy in the fanfiction. Maybe some dark wizard or witch sent a spell his way before he boarded the train, and it took effect during the journey.
His friends Ron and Hermione would likely be the first to find him. They are always by his side in most situations. They know Harry well and would notice if he was in trouble.
Maybe a jealous student from Slytherin who wants to get back at Harry Potter and his friends. This student discovers a dark and forbidden spell that creates a bondage effect. They start using it on the Hogwarts Express to cause chaos and make Harry and his friends look bad. They see themselves as an antagonist because they feel wronged by Harry and his group in some way, and this is their way of getting revenge.
In a Hufflepuff - related fanfiction, the Hufflepuffs could be the ones to welcome the Lemon Fairy with open arms. They would be kind and inclusive, perhaps inviting the fairy to stay in their common room. The fairy could then help the Hufflepuffs in their tasks, like using its magic to make the Hufflepuff's plants grow better in their little garden area near the kitchens.
If Naruto were truly dominated by this type of fanfiction, it could be a negative in some ways. It might overshadow the more positive and original aspects of the Naruto fanfiction world that are based on the core values of the series, like friendship, perseverance, and self - improvement. However, it also depends on how one views different types of fan - created content.
Lemon could impact the events in Hogwarts by being a role model for younger students. If she is older and more experienced in magic, she might start a club or study group to help others improve their skills. This could lead to a more united Hogwarts student body, as students from different houses come together to learn from her.
Another type of all - age - appropriate fanfiction could be those that explore the backstories of the minor characters at Hogwarts. Maybe the story of how Neville Longbottom overcame his insecurities before the big battles. It adds depth to the Hogwarts world and is a positive alternative to inappropriate fanfiction.
There are quite a few fanfictions in this category. Some focus on how their relationship might develop secretly at Hogwarts. For example, 'Hidden Desires at Hogwarts' could be one. In these fanfictions, the authors usually create scenarios where Harry and Hermione's feelings for each other intensify in the familiar halls and classrooms of the school. They might face challenges from other students or the school's rules while their relationship blossoms.