You could write a Lion King fanfic about the backstory of Scar. How did he become so bitter? What were his early experiences in the pride that led him to envy Mufasa? Maybe he had a difficult childhood or some event that made him feel inferior, and exploring these aspects could make for an interesting story.
One idea could be to explore what would happen if Simba had a different mentor. For example, instead of Rafiki, it could be a new character who teaches him a different way of leadership. Another idea is to create a story where the hyenas reform and try to integrate into the pride. Maybe they realize the error of their ways after Scar's downfall and want to make amends.
A fanfic could focus on the relationship between Nala and Simba from a different perspective. Instead of the typical love story, it could be about their friendship first. How did they support each other as cubs? What adventures did they have that strengthened their bond before they realized their romantic feelings?
One idea could be an anthro version where the characters are in a modern-day city. Simba could be a young entrepreneur trying to make his mark in the business world while still dealing with the legacy of his father. Another could be an anthro story where the animals form a sort of United Nations - like organization to deal with inter - species conflicts. For example, the lions, hyenas, and other animals come together to discuss territory and resource sharing.
One idea could be a crossover where Harry Potter characters visit the Pride Lands. For example, Hermione could use her magic to help solve some of the problems in the Lion King's world, like finding a new water source during a drought. Another idea is that Simba could be sent to Hogwarts for some reason and has to learn magic while dealing with the Hogwarts politics. Maybe the Sorting Hat has a hard time deciding which house to put him in because he has qualities of all the houses.
One idea could be creating an OC (original character) who is a long - lost relative of Simba. This OC could arrive in the Pride Lands with a unique skill, like being able to communicate with a different type of animal that the lions usually don't interact with. For example, a small rodent that has knowledge of a hidden danger approaching the Pride Lands.
A fanfiction could also be about the hyenas getting a second chance. Maybe they find a new place to live and try to form a more positive community, with some help from the lions.
Some great concepts for human Lion King fanfiction could involve a human being adopted by a lion pride. This human grows up with the lions, learning their language and customs. They could then use their human intelligence to come up with new strategies for hunting or defending the pride. For example, they might introduce the concept of traps to catch prey more efficiently. Another idea is a human who is a storyteller in the human world but somehow ends up in the Lion King world. The human then tells the lions stories from their own world, which inspire the lions to be better leaders or to face their fears. Also, a human with magical powers could arrive in the Pride Lands and use their powers to heal the land that has been damaged by Scar's reign.
Another possibility is a human who has a special power, like being able to communicate with all animals. They come to the Pride Lands during a time of trouble, such as a drought or an invasion from another group of animals, and use their power to help the lions and other creatures.
One idea could be to explore the relationship between Kiara and Kovu in a human setting. Maybe they meet at a high school where there are different social groups and they have to overcome the prejudice between their 'pride' - like the popular kids and the outcasts. It could add a modern twist to their classic love story.
One idea could be exploring what would happen if Simba had a long - lost sibling. Another could be a story where Scar had a change of heart before his final battle with Simba. Maybe a fanfiction about the animals in the Pride Lands having to deal with a new, unknown threat that even Mufasa didn't foresee.
One idea could be creating an OC who is a lost cub from a different pride. This cub could bring new perspectives and skills to Simba's pride. For example, it might know special hunting techniques or have a unique way of communicating with the other animals in the Pride Lands.
Well, in Lion King lemons fanfiction, you could focus on the hyenas. For example, how their lives might have been different if they hadn't been so closely associated with Scar. You could also write a story about how the animals in the Pride Lands deal with a strange new plant that has some 'lemons' - like effects on their behavior. And perhaps a story about Mufasa's spirit interacting with the current Pride Lands in a rather humorous and lemons - filled way.