One idea could be that they go on a secret mission together outside of their usual group activities. They face various challenges and in the process, their relationship deepens as they rely on each other's skills.
Another plot could involve Makoto getting into some sort of trouble that only Joker can help her out of. Maybe she's being blackmailed by some shadowy figures in the Metaverse. Joker steps in to save her, and during their adventure to take down the blackmailers, they grow closer and their bond becomes unbreakable.
Perhaps in the fan fiction, Joker and Makoto could be paired up for a school project. As they work on it, they discover new things about each other. Makoto might learn about Joker's more carefree side, and Joker could see Makoto's determination in a different light. They start to develop feelings as they spend more time together.
A plot could involve the Joker creating a new type of toxin that doesn't just affect people's physical state but also their perception of reality. Batman has to race against time to find the antidote while also dealing with the chaos in Gotham caused by the affected citizens. Or perhaps a story where the Joker discovers Batman's true identity in a very unexpected way and uses it to manipulate those closest to Bruce Wayne, forcing Batman to face a whole new level of personal and public danger.
Another plot could be a role - reversal. The Joker gets hit by some strange gas that makes him lose his 'evil' side for a while. Harley then has to deal with a very different Joker, and she starts to miss the old him in some ways while also enjoying this new side of him. It could be a story of self - discovery for both of them.
First, you need to understand the characters well. Know their personalities, strengths, and weaknesses. For example, Joker is often seen as a bit of a rebel, while Makoto is more of a rule - follower. You can use this contrast to create interesting interactions between them.
One idea could be a story where the Mandalorian has to team up with an old enemy to fight a new, greater threat. Maybe a powerful Sith Lord emerges and they have to put aside their differences.
One idea could be exploring a different origin for Toothless. Maybe he was part of an ancient dragon tribe that was thought to be extinct. Another could be a story where Hiccup discovers a new dragon species that has unique abilities and forms an alliance with them. A third idea is a time - travel fan fiction where Hiccup goes back in time to prevent a great dragon war from ever starting.
A great plot for Warframe fan fiction could be a Tenno getting trapped in a parallel dimension where the rules of the Origin System are all messed up. They have to find a way back while dealing with strange versions of familiar enemies. Or perhaps a story about a Tenno who discovers a hidden Orokin vault that contains not only powerful weapons but also a secret that could change the balance of power in the Origin System. Also, a plot about a Tenno's struggle to control a newly acquired and extremely powerful Warframe that has a mind of its own could be really engaging.
Well, you could have a survivor fan fiction where a contestant has a hidden skill, like being able to communicate with animals on the island. This could give them an edge in finding food and avoiding danger. Or perhaps a story where there's a traitor within the group, someone who is secretly working with the show's producers to create more drama. Also, a plot where the survivors find a map that leads to a hidden part of the island with a bountiful supply of food and shelter.
One idea could be that the Ghostbusters discover a new type of ghost that can possess technology. So they have to find a way to stop it from taking over all the electronics in the city. It would be a race against time as the city starts to descend into chaos with machines going haywire.
One idea could be a story where a minor character from the game gets a chance to become a hero. For example, a low - level soldier who discovers a hidden power within himself and uses it to save his comrades during a crucial battle.
One interesting plot idea could be exploring what would happen if Aladdin's three wishes had unforeseen consequences that affected not just him but the whole city. For example, a wish for wealth might lead to an economic imbalance.