One characteristic is that they often explore Orochimaru's complex personality. Since he is a morally ambiguous character, fanfics usually dig deeper into what makes him tick. Another is that they might introduce new and unique plotlines related to his experiments or his search for power.
Since Orochimaru had many experiments and secrets, his death at Naruto's hands in the Chunin Exams fanfiction could lead to a scramble for his research. Other villages or even some rogue ninjas might try to steal his notes and facilities. In Konoha, Naruto might be pressured to reveal what he knew about Orochimaru's plans and secrets. This could put him in a difficult position as he may not know everything. Also, Sasuke, who had a connection with Orochimaru, might have a complex reaction. He could be angry at Naruto for killing Orochimaru, or he could see it as a sign of Naruto's strength and be motivated to become stronger himself.
A good young Orochimaru fanfiction often has a well - developed character of Orochimaru. It should explore his motives, his early days in the ninja academy, and his relationships with other characters like Hiruzen Sarutobi. The plot should be engaging, perhaps with a unique take on Orochimaru's path to becoming the villain we know in the Naruto series.
In a fanfiction like this, the author might play with the idea of power dynamics. Orochimaru is a powerful and cunning shinobi, and Tsunade is not only strong but also a medical ninja with great influence. The "lemon" aspect could be used to show a different side of their relationship, perhaps a moment of weakness or a strange connection that forms during a difficult situation. However, this is all speculation as such fanfictions are not part of the mainstream Naruto narrative.
One common theme is power and ambition. Since Orochimaru is known for his pursuit of power, the OC often gets caught up in that. Another is the exploration of the dark side of the ninja world. Orochimaru is a rather dark character, so the OC may have to deal with moral gray areas. And there's also the theme of self - discovery. The OC in these fanfictions usually has to figure out who they are in relation to Orochimaru and the world around them.
One possible plotline could be a more metaphorical 'pregnancy' in the sense of Orochimaru creating or nurturing a new and powerful jutsu or experiment that is like a 'baby' to him. It could show his obsessive nature in a different light, as he devotes all his time and resources to this new creation.
It could be about Fem Orochimaru having a different relationship with Naruto. Maybe she sees him as a potential ally or apprentice in a new way compared to the original Orochimaru.
One possible plot is that Orochimaru needs Sakura's medical skills for one of his experiments. He kidnaps her and forces her to be his apprentice. Sakura initially resists but realizes that she can learn a great deal from him. As she becomes more involved in Orochimaru's world, she starts to form her own plans. She could be secretly working on a way to use Orochimaru's resources to develop a cure for a deadly disease in the ninja world. But she has to keep her true intentions hidden from Orochimaru, leading to a tense and complex plot full of twists and turns.
One interesting Orochimaru in Fairy Tail fanfiction could be one where he is a hidden villain within the Fairy Tail guild, secretly manipulating events from the shadows. He might be using his snake - like abilities in new and unexpected ways within the Fairy Tail world.
Perhaps the fanfic could be about an Orochimaru's student who is sent on a secret mission. On this mission, they meet different characters who make them question their loyalty to Orochimaru. They could also find a hidden power within themselves that is not related to Orochimaru's teachings. This new power could be the key to their redemption or a new path away from Orochimaru.