Maybe in the 'my gym partner's a monkey fan fiction', the monkey has a magical ability. Every time the human partner is feeling down or tired during a workout, the monkey touches him and gives him a burst of energy. The monkey could also be on a secret mission in the gym. He's looking for a lost treasure that he believes is hidden somewhere in the gym. So while they're working out, the monkey is constantly searching for clues, which makes for an exciting and mysterious fan fiction.
You can start by creating a character profile for the monkey. Decide on its personality traits, like whether it's mischievous or really friendly. Then, describe the first encounter between the human and the monkey in the gym. Maybe the monkey jumps on the treadmill next to the human and starts running in a really funny way. This initial scene can set the tone for the whole fan fiction.
One idea could be to create an alternate universe where the hero's powers are reversed. For example, if the hero can usually fly, in this AU they might be afraid of heights. Another idea is to write a story about the hero's origin from a different perspective, like that of a bystander who witnessed the events that led to them becoming a hero. You could also explore a relationship between the hero and a minor character in the original story, developing it in a new and unexpected way.
One idea could be a story where 2B and 9S have to survive in a post - apocalyptic world without their usual support systems. They rely on each other more than ever, facing new and unknown threats.
One interesting aspect in Harry Potter gym fanfiction can be the creation of magical gym equipment. Picture a treadmill that can transport you to different magical landscapes as you run, or a set of weights that adjust themselves based on your magical energy level. Also, there could be a plot where the gym becomes a place for inter - house competitions, not just in Quidditch but also in physical and magical fitness, leading to new friendships and rivalries among the students.
A great plot for My Hero Academia fan fiction is exploring the backstories of the teachers. What if Aizawa had a secret mission during his early hero days that changed his view on heroics? Another idea is to create an alternate universe where quirks are reversed. So, someone like Bakugo who has an explosive quirk now has a quirk that absorbs explosions. Also, you could write a story about a new student with a really strange and powerful quirk that no one understands, and they struggle to fit in while also being a target for villains.
One idea could be to have the main character discover a hidden cave filled with ancient Native American artifacts. This would add a new layer of mystery and adventure to the story.
One idea could be to explore the backstory of an unnamed assassin in the game. Maybe they have a personal vendetta against a particular Templar that goes beyond the main plot. Another idea is to create a fan fiction where the Assassins and Templars have to team up temporarily to face a greater threat, like an ancient evil that's been awakened.
One idea could be exploring the backstories of each member of Haven's Nine in more detail. Maybe one of them has a secret past as a lost heir to a powerful family. Another idea is to create a story where they face a new and extremely powerful enemy that forces them to develop new skills and strategies.
One interesting idea could be exploring the backstories of the alien races in the game. For example, you could write about how the Gek evolved and what their society was like before the events of the game. Another idea is to create a story about a lost traveler who discovers a hidden part of the universe that has unique planets and creatures not yet known in the main game. Maybe a story where a character tries to build a utopia on a desolate planet by using the in - game mechanics in creative ways.
In 'the sorcerer's apprentice fan fiction', you could also introduce new magical creatures. The apprentice could befriend a magical creature that helps him in his studies or in times of trouble. Additionally, you could explore what would happen if the apprentice accidentally cast a spell that sent him back in time. He would have to use his limited knowledge of magic to get back to his own time while also not changing the course of history too much.