One interesting fanfiction could be where Lucy discovers she has a unique magical ability that even Harry doesn't have. Maybe she can communicate with magical creatures on a deeper level. In this story, she uses her ability to solve a mystery in Hogwarts that has been baffling everyone. It could show her growing up in the shadow of her famous brother but still making her own mark in the wizarding world.
A recurring theme might be the struggle for acceptance. People might have certain expectations of her because she's related to Harry. Some might expect her to be just as brave or talented as him, while others might be jealous or suspicious. So, the fanfiction could focus on how Lucy deals with these different attitudes and tries to be accepted for who she really is in the wizarding community.
One common theme is family. Since it's about Harry having a little sister, it often explores the family dynamic. How they support each other, protect one another, and sometimes even have sibling rivalries. Another theme is identity. The little sister has to figure out who she is in the shadow of her famous brother.
Voldemort's remaining followers could be antagonists. They might target Harry's little sister thinking they can use her to get to Harry. They could try to kidnap her or use dark magic on her.
In a 'Harry Potter and His Little Sister' fanfiction, the sister could be a new student at Hogwarts when Harry is in his later years. She struggles to fit in because of being Harry Potter's sister. Harry has to help her deal with the pressure, make friends, and also face the threat of a new dark wizard who has a vendetta against the Potter family.
You can start by looking on fanfiction websites like Archive of Our Own (AO3). Just search for 'Lucy Pevensie little sister' in the search bar, and it should bring up a bunch of relevant stories. There are often tags and filters you can use to narrow down the results, such as the genre you prefer, like adventure or friendship based stories.
One common theme is family dynamics. Since she's seen as a little sister, there are often stories exploring her relationships with her siblings in more depth, like how they protect her or how she tries to prove herself to them. Another theme is growth. Lucy might be portrayed as growing up in Narnia, learning more about the magical world and her place in it as a little sister.
One great Harry Potter little sister fanfiction is 'The Potter Siblings' on FanFiction.net. It delves into the relationship between Harry and his fictional little sister in a really heartwarming way. The story shows how she grows up in the shadow of her famous brother yet manages to carve out her own identity within the wizarding world.
Well, obviously the little sister herself is a very important character. Depending on how she's written, she could be really kind - like a Hufflepuff at heart - or really brave and adventurous like a Gryffindor. Then there are the classic characters from the original series that often play a big role. Hermione would likely be there to offer her wisdom and help the little sister with her studies. Ron would be the comical friend, always getting into some sort of trouble but also being very loyal.
One idea could be that Lucy's little sister has a special magical ability that is different from Lucy's. For example, while Lucy uses celestial spirit magic, her sister could have nature - based magic. In the fanfiction, she might start out as a bit of an outcast in the guild because her powers are so different, but then she gradually earns everyone's respect through her determination and kind heart.