One common theme is friendship. Since they are from different 'worlds' (in the context of their original stories), a lot of fanfictions focus on how they overcome their differences to become friends.
Love is a very common theme. It could be the budding of a new love or a deep, long - lasting love. Another common theme is friendship. Since they are often in the same circle, their friendship is explored and how it might develop into something more.
One common plot is a human becoming friends with a member of Loona and going on adventures together. For example, they might explore a magical world that only the Loona member knows about. Another plot could be a love story where a human falls in love with a Loona member and they have to overcome differences, like the fact that one is from a different species or a famous idol while the other is an ordinary human. There are also plots where the human helps the Loona group solve a problem, like a mystery related to their music or a threat to their group.
One common theme is friendship turning into something more. For example, they start as just fans or acquaintances and then develop deeper feelings. Another theme is the exploration of the idol - fan relationship in a more personal and emotional way.
One common plot element is the meet - cute. It could be at a concert, a fan - meet, or just by chance on the street. Another is the reader helping a LOONA member through a difficult time, like dealing with the pressures of idol life.
One popular 'loona x octavia fanfiction' is 'The Unlikely Bond'. It explores how their different personalities from their respective universes collide and form a unique friendship. It has really well - written dialogue that brings the characters to life.
Another theme is the contrast between their personalities. Moxxie is more reserved and proper while Loona is brash and moody. Fanfics play with this difference, showing how they either clash because of it or find a way to complement each other. For example, in some fanfics, Moxxie's calmness helps soothe Loona's temper, and Loona's boldness encourages Moxxie to be more adventurous.
Love and romance can be a theme as well, although not in all. Some fanfics explore the romantic feelings that might develop between Loona and the reader. This can be a slow - burn kind of romance, where they first get to know each other on a deeper level before any romantic feelings surface.
Sure. You can check out Archive of Our Own (AO3). There are a lot of great loona x reader fanfics there. Just search for 'loona x reader' in the search bar and you'll find a variety of stories with different themes and writing styles.
I don't know for sure. To figure out if Millie is a real story, we'd need to know more about the plot, the source, and any background information available.