One common theme is friendship evolving into something more. Maybe the fem reader starts off as a friend to Jean Grey in the X - Men world, and then they gradually develop deeper feelings for each other.
Sure. You can check out Archive of Our Own (AO3). There are a lot of great 'jean grey x fem reader fanfic' there. Just search for the tag and you'll find a variety of stories with different themes and writing styles.
Another theme is the struggle between normalcy and the extraordinary. The male reader is usually an ordinary person thrust into Jean Grey's world of mutants and powers. This contrast can lead to themes of acceptance, not just of Jean but also of the strange new world the male reader finds himself in.
One popular 'Jean Grey x Male Reader' fanfic is 'A Bond Beyond Powers'. It focuses on a unique relationship where the male reader character has to navigate the complex world of Jean Grey's powers and her emotional state. The story is filled with interesting character interactions and a bit of adventure.
One common theme is the discovery of self. The OC often goes through a journey of self - discovery while interacting with Jean Grey. For example, they might learn about their own powers or their place in the world because of their relationship with her.
One major theme is the struggle between the OC's normal life and the extraordinary world of mutants that Jean Grey represents. Also, themes of acceptance are quite common. The OC may face discrimination, and Jean Grey helps them through it. For example, in some fanfics, the OC is a mutant with a very visible mutation, and Jean Grey uses her telepathy to help the OC accept themselves. It can be a very emotional and relatable theme. There are also fanfics that revolve around the theme of sacrifice, where either the OC or Jean Grey has to make a difficult choice to save the other or the entire mutant community.
I really liked 'A New Perspective'. In this fanfic, the OC brings a fresh outlook to the X - Men universe, especially in relation to Jean Grey. It has some really interesting plot twists and character developments. The way the author portrays the connection between the OC and Jean is both engaging and thought - provoking.
One possible plot could be that the OC is a new mutant who arrives at the X - Men school. Jean Grey senses a powerful and unique energy within the OC. Scott is initially cautious but as they all train together, the OC starts to develop feelings for both Jean and Scott. Meanwhile, a common enemy emerges that forces them to work closely, and during this time, a complex love triangle forms as Jean and Scott also find themselves drawn to the OC in different ways.
Mr. Sinister could be a great antagonist. He might be interested in the OC's unique genetic makeup, which could be related to Jean and Scott's powers in some way. He could try to manipulate the situation to his advantage, perhaps by pitting Jean and Scott against each other over the OC, or by trying to turn the OC against them.
Well, it could be about the OC having some unique power that Jean Grey senses and they end up teaming up. Maybe the OC is from a different dimension and Jean helps them adapt to the X - Men's world.