A really cool plot twist could be that the fourth hokage was not really Naruto's biological father but was instead given Naruto to protect by some higher power. This would then lead to a search for Naruto's real parents and a whole new set of adventures and revelations about the Naruto world's secrets.
One interesting plot twist could be that the fourth hokage didn't actually die when he sealed the nine - tails in Naruto. Instead, he was trapped in a sort of limbo within Naruto's mind and could communicate with him at crucial moments, guiding him in ways that no one else could understand.
In some fanfictions, it might be a plot twist that Naruto discovers he has a special power passed down from his father that was not just the nine - tails. For example, a unique form of space - time ninjutsu that was kept secret. This would change the power dynamics in the Naruto universe and give him an edge against his enemies in a completely unexpected way.
One interesting Naruto Fourth Hokage fanfiction could be one where he survives the fight against the Nine - Tails. In this kind of fanfiction, he gets to see Naruto grow up and train him personally. It would be a heartwarming story of a father - son relationship that was cut short in the original series.
One possible plot twist could be that Naruto has to face an unexpected enemy from the past of the Fourth Hokage. Maybe a hidden group that was against Minato's policies and now they see Naruto as a threat. Another could be that Naruto discovers a new jutsu that Minato was developing but never completed, which changes the power dynamics in the village.
One possible plot twist could be that the second Hokage had some secret enemies who target Naruto because of his lineage. Another could be that Naruto discovers some hidden jutsu or power that was passed down specifically from the second Hokage. Maybe there's a twist where the village initially rejects Naruto because they believe the second Hokage had some dark secrets that they fear Naruto might inherit.
In some fanfictions, a great plot twist is when Draco is on the verge of making a really bad decision, like joining the Death Eaters completely. But then he discovers his true relation to Severus. This changes his perspective as he realizes Severus has been secretly protecting him all along. It makes him question his loyalty to the Dark side. Also, there could be a plot twist where Severus has to choose between his loyalty to Dumbledore and protecting his son Draco, which creates a lot of internal conflict for him.
In some fanfictions, a cool plot twist could be that Percy's connection to Kronos gives him the ability to travel through time. He could use this power to go back and change certain events that led to Kronos' rise or fall. But this also comes with risks, like accidentally changing things for the worse or getting trapped in a different time period.
A great plot twist could be that Serafall's enemies target Naruto because of his relation to her. This would put Naruto in a whole new set of dangerous situations and force him to learn new skills or rely on his mother's (Serafall's) powers in unexpected ways. Another plot twist might be that Naruto discovers some long - hidden secrets about his real father, which could completely change his perception of himself and his place in the world. There could also be a plot twist where Naruto's presence in Serafall's world causes political unrest or changes in the power dynamics of the devil realm.
One interesting plot twist could be that Naruto discovers a hidden prophecy about the Hokage that changes his entire perception of the role. He might find out that the Hokage is meant to make a great sacrifice for the village in a way he never expected.
One interesting plot twist could be that Naruto discovers he has a long - lost sibling from another village. This would completely change the dynamics of his relationships and his understanding of his own family. Another could be that Sasuke turns out to be the key to a new and powerful jutsu that was sealed away long ago, forcing Naruto to team up with him in a whole new way.
In this fanfiction, the plot might involve Naruto being tricked by an evil force into believing that the Fourth Hokage has some dark secrets. So he decides to fight him. It could also be a scenario where Naruto enters a different dimension where the Fourth Hokage is being controlled by an outside power, and Naruto has to free him by fighting. And during the fight, Naruto discovers new things about his father and his own abilities.
One interesting plot twist could be that some of the dead ninjas from previous wars come back not as enemies but as allies with a secret mission to end the cycle of hatred. They might have gained new powers or knowledge in the afterlife that can turn the tide of the Fourth Great Ninja War.