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.
A plot twist might be that they both get captured by a third party. This could be a group of rebels or a new, unknown force in Westeros. Trapped together, they are forced to rely on each other to escape. In the process, they learn more about each other's pasts and what has driven them to their current positions of power. This could lead to a change in their relationship, from enmity to a begrudging alliance.
In such a fanfiction, they might initially be hostile. Daenerys, with her dragons and army, could pose a huge threat to Cersei. Cersei, being the shrewd and power - hungry character she is, would likely try to outwit Daenerys. Maybe there would be some intense verbal sparring between them as they both try to assert their dominance over King's Landing.
One possible plot twist could be that Arya, being a master of disguise, infiltrates Daenerys' court under a false identity. She initially plans to spy on the Dragon Queen but ends up being impressed by Daenerys' leadership and her quest for justice. This could lead to an unexpected alliance between the two strong - willed women.
Well, a really interesting plot twist in 'Mario Meets Peach Fanfiction' could be that Mario himself is the one being tricked. Bowser has created a fake Peach to lure Mario into a trap. And while Mario is busy trying to rescue the fake Peach, the real Peach is actually in another location, in even greater danger. Also, there could be a plot twist where the power - ups that Mario usually relies on are actually cursed this time. When he uses them, they cause more harm than good. Maybe the super mushroom makes him too big to fit through the narrow passages he needs to reach Peach. Another possibility is that Peach has fallen in love with someone else in the time she has been captive, and Mario has to deal with this new emotional situation.
A possible plot twist could be that Videl turns out to have some hidden powers herself. It would completely change the dynamic between her and Gohan.
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.
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 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.
A plot twist might be that Videl is actually related to one of Gohan's enemies in some way. This would create a huge conflict between them. Also, it could be that there is a prophecy about Gohan and Videl that they are not aware of, and when they find out, it completely changes their relationship. Maybe Gohan loses his powers temporarily, and Videl has to protect him, which is a role reversal from what is expected in the DBZ world.