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.
One possible plot twist could be that Bella, as a Mikaelson twin, discovers a hidden power within herself that is different from the other Mikaelsons. Maybe she has a unique connection to nature, like being able to control certain elements. Another twist could be that she is actually a key to an ancient prophecy that the Mikaelson family has been trying to figure out for centuries. This would put her in a central position in the family's power struggles and relationships. And perhaps she finds out that she was switched at birth and her real family is someone completely different, which would create a whole new set of conflicts and emotional turmoil within the story.
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.
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.
Another plot twist might be a time - related one. What if John gets transported back in time to the events of the Harry Potter series and meets a younger Hermione? His different perspective and knowledge from his own world could change the course of events in the wizarding world, creating a complex web of changes and consequences.
In some fanfics, a plot twist could be that Severus was actually protecting Hermione all along under Dumbledore's secret orders, and Sirius discovers this and has to re - evaluate his hatred for Severus. This completely changes the dynamic between the three.
One interesting plot twist could be that Naruto starts to have memories of Tobirama's past battles. This would make him question his own identity and purpose. Another could be that Tobirama's reincarnation in Naruto causes a shift in the power dynamics among the villages. It might make other villages see Konoha as a greater threat or as a source of new knowledge.
One of the most interesting plot twists could be that Naruto discovers a new form of chakra that has the power to rewrite history. This would completely change the power dynamics in the Naruto universe.
One interesting plot twist is that the chakra seal on Naruto is actually a key to an ancient power source. At first, it seems like a hindrance, but as the story progresses, it's revealed that the seal was placed there to protect this power until Naruto was ready. This flips the whole concept of the chakra seal from a negative to a positive in an unexpected way. Also, there could be a plot twist where the sealing of Naruto's chakra was a misdirect, and it was actually someone else's chakra that was being targeted, and Naruto was just a decoy.
In 'Frozen Bonds', the plot twist is that the Snow Queen has been manipulating events all along not for evil, but to protect Emma from a greater threat that she is unaware of. This flips the typical villain - hero perception on its head and makes for a really unique and thought - provoking story.
One possible plot twist could be a character from 'Twilight' getting superpowers like those in 'Heroes'. For example, Bella could suddenly gain the ability to fly or become invisible. This would completely change her dynamic within the 'Twilight' world and her relationship with Edward and Jacob. Another twist could be a 'Heroes' character becoming a vampire or a werewolf. It would introduce new challenges and moral dilemmas as they deal with their newfound nature.