Well, in this fanfiction, a major plot twist could be that the Dursleys are part of a secret society that has been observing the wizarding world all along. Hermione stumbles upon this fact when she meets them. This would completely change her perception of them. Also, it's possible that Hermione's presence at the Dursleys' house somehow triggers a long - lost magic within the house itself. This magic could be either good or bad, and Hermione has to deal with the consequences, all while trying to interact with the Dursleys who are also caught up in this strange new situation.
One possible plot twist could be that the Dursleys are actually under a spell that makes them act so horribly, and Hermione discovers and breaks it. Another could be that Hermione finds out she has some family connection to the Dursleys, which would be a huge shock for everyone.
In such a fanfiction, Hermione's encounter with the Dursleys could be full of drama. Since Hermione is a clever witch, she may use her magic knowledge to expose the Dursleys' ill - treatment of Harry. For example, she could magically make Dudley see how wrong his parents' actions are. At the same time, she may also try to bridge the gap between the wizarding world and the Dursleys, though it would be a difficult task considering the Dursleys' deep - rooted dislike for anything magical. However, Hermione's determination might bring some unexpected changes to the Dursleys' household.
A big plot twist could be that Draco's discovery about the Dursleys makes him the target of some dark forces. These forces don't want the truth about the Dursleys' treatment of Harry to be known. So, Draco has to fight not only for Harry's sake but also for his own survival. This would turn the story into a more action - packed and dangerous adventure for Draco.
A plot twist might be that Jotaro loses his Stand abilities temporarily and McCree has to protect him. Or perhaps they find out that there's a traitor among the people they thought were their allies in this fanfiction world. This would force them to re - evaluate their situation and who they can trust. Also, it could be that a powerful artifact they were supposed to protect actually has the power to control them, and they have to fight against its influence.
One possible plot twist could be that Cersei pretends to surrender to Daenerys. Daenerys, believing her, takes Cersei into her confidence. But Cersei is actually plotting a big betrayal from within. She could be secretly gathering her remaining forces and planning to assassinate Daenerys when the time is right.
In the 'naruto meets nagato fanfiction', a plot twist might be that Nagato fakes his change of heart at first. He could be playing a long - game to deceive Naruto and the Leaf Village. Or perhaps, there is a prophecy that involves both of them, but it has been misinterpreted all along. And when they meet, they start to uncover the real meaning of the prophecy, which changes everything they thought they knew about their fates and the future of the ninja world.
One possible plot twist could be that Bowsette turns out to have some sort of connection to Naruto's world that he never expected. Maybe she has a hidden kekkei genkai - like ability that is related to Naruto's ninja powers.
A possible plot twist could be that the dragon is actually a shapeshifter and turns into a human form that Shirou knows. Maybe it's someone he thought was dead.
One possible plot twist could be that Hermione's pureblood status was hidden to protect her from a dark wizard or an old family feud. When the truth comes out, she has to face unexpected enemies.
One possible plot twist could be that Underfell Sans turns out to be a long - lost relative of one of the Underswap characters. Another could be that a villain from Underfell follows him to the Underswap world and causes chaos. Or perhaps Underfell Sans is actually there to steal something important from the Underswap world but has a change of heart halfway through.
One possible plot twist could be that Paul is actually working for an enemy of Bella's family in secret, and his initial meeting with Bella was part of a plan. But then he starts to have real feelings for her and has to decide between his loyalty to his side and his new - found feelings.