Well, sometimes in these fanfictions, the reborn Ultron might find out that it was created with a hidden purpose by an even more shadowy figure. This discovery could lead it on a journey to uncover the truth about its origin, and along the way, it has to decide whether to continue its vendetta against the Avengers or not. It's really interesting to see how the writers play with this concept of self - discovery.
Perhaps the character is reborn with memories of a future event that threatens the Mikaelsons. This would put them in a position to either try to change the future or use it to their advantage within the family dynamics. They might face disbelief from the Mikaelsons at first, but as events start to unfold as they remembered, they gain more influence.
A possible plot twist is that Naruto, reborn as Itachi, uses his knowledge of future events to change the Uchiha clan's fate. He could try to expose the real masterminds behind the planned Uchiha coup and prevent the massacre. This would completely change the course of the story, not just for the Uchiha but for the entire ninja world. Also, his relationship with other characters like Kakashi would be very different. Kakashi, who had a certain view of Itachi, would now be dealing with a Naruto - influenced Itachi.
A really cool plot twist in Hermione as a Marauders' daughter fanfictions is when she realizes that her real mother was a powerful witch who was erased from history by some dark force. This makes her quest not only about finding her place as the Marauders' daughter but also about restoring her mother's name. Another plot twist could be that the Marauders had some sort of magical pact that is now passed on to Hermione. This pact might force her to make difficult choices between her loyalty to her new - found family and her friends. And sometimes, there's a plot twist where Hermione discovers that she has a twin sister who was separated from her at birth, and this sister has been living in the shadows, also with a connection to the Marauders, which throws a whole new set of challenges her way.
Another possible plot twist is if the Forerunners from Halo are somehow related to the ancient magic in Familiar of Zero. Maybe they left behind some technology or knowledge that is now perceived as magic in the Familiar of Zero world. This would open up a whole new avenue of exploration for the characters, as they try to understand the true nature of their powers and the connection between the two universes.
Perhaps in some fanfictions, a major villain from 'Worm' teams up with a powerful organization from 'Darker than Black'. This alliance could lead to a whole new set of challenges for the heroes of both universes. They would have to put aside their differences and find a way to combat this unexpected union. This plot twist not only changes the power dynamics but also forces the characters to grow and adapt in new ways.
Perhaps in some fanfictions, the past reveals that there was a secret alliance between the Leaf Village and an enemy village long ago. And in the future part of the fanfic, this alliance resurfaces and creates a whole new dynamic among the characters. It might lead to Naruto having to make difficult choices between loyalty to his own village and this newfound connection.
One common plot twist could be that they initially seem to be enemies but are actually long - lost brothers. Another might be that they both get caught in a strange alternate universe where their roles are completely reversed. And a third could be that an outside force tries to make them fight, but they end up teaming up against it.
A really interesting plot twist could be around the Half - Blood Prince himself. The fanfiction could explore the idea that the identity of the Half - Blood Prince was misinterpreted in the original book. Maybe it was a red herring, and there was someone else who was the true 'Half - Blood Prince' all along, with a completely different set of motives and actions that would have a major impact on the story.
In some fanfictions, like 'The Unforeseen Consequences of Time Travel', a plot twist could be that when Harry and Hermione go back in time to save someone, they end up causing more harm than good. This completely flips the expected outcome on its head and makes for a very engaging read.
One really cool plot twist in 'One More Day' Spider - Man fanfictions is when an alternate version of Peter Parker from another dimension arrives. This other Peter has his own set of experiences and morals, and he challenges our Peter's decisions regarding the 'One More Day' situation. He might show Peter that there are other ways to deal with his problems, like finding a way to keep his marriage and still save Aunt May without making a deal with Mephisto. It adds a whole new layer of complexity to the story.