Well, he might start being more mysterious like Tobi. He could start using more deception in his actions, for example, hiding his true intentions from his friends just as Tobi often did. Maybe he'll also start using some of Tobi's speech patterns or ways of interacting with others in a more indirect and puzzling way.
Well, in this fanfiction, it could be that Harry Potter has come across some sort of ancient magic or artifact that has changed him. Maybe this magic has a connection to Tobi's essence or the type of power that Tobi wields. Additionally, he might be trying to protect his friends in a different way. Tobi has his own way of safeguarding what he holds dear, which might seem appealing to Harry in a difficult situation. Or, there could be a prophecy or a hidden message that he has misinterpreted, leading him to believe that acting like Tobi is the right path to take.
Maybe he's on a secret mission. He could be trying to infiltrate an enemy group that Tobi was associated with. By acting like Tobi, he hopes to gain their trust and gather information.
In the 'harry potter acts like tobi fanfiction', Harry Potter's behavior could change in several ways. Tobi is known for his ability to manipulate situations to his advantage. So, Harry might start using his knowledge and skills in a more calculating way. For example, he could be more strategic in his interactions with his friends and enemies alike. Instead of being straightforward, he might play mind games like Tobi does. He could also become more solitary, as Tobi often keeps to himself, and only reveals his true intentions when it suits him. This would be a significant departure from Harry's more open and honest nature in the original series.
In a 'naruto acts like gin fanfiction', Naruto might be quieter and more observant. Instead of his usual boisterous self, he could be more like Gin, who is often sly and calculating. Maybe he would have a more subdued way of showing his power and a different approach to his enemies.
The fanfiction could explore Naruto being in a situation where he has to act like Madara to deceive the enemy. He gradually gets too deep into the role and starts to actually think and act like Madara on a more permanent basis. His friends notice the changes in his personality, like his increased aggression and his new - found belief in power as the ultimate factor in achieving goals. They then try to bring the old Naruto back.
One possible plot could be that Naruto, after being exposed to some strange chakra or magic, starts to take on Grimmjow's aggressive and fearless attitude. He might become more impulsive in battle, like Grimmjow, and start to challenge his enemies without much thought for strategy at first. His friends would be confused by this sudden change in his behavior.
Well, one possible plot could be that Naruto starts to adopt Pain's view on justice. He might see the world as a place full of suffering that needs a radical change. He could begin to question the traditional ways of the Hidden Leaf Village and try to implement some of Pain's ideas in a more positive way, like finding a new system to ensure peace that doesn't rely solely on the power of the ninja villages.
If Naruto were to act like Yujiro in a fanfiction, it would change his relationships too. He would no longer be the overly - friendly Naruto we know. He might become more aloof and selective with his friendships. His interactions with Sasuke could be different. Instead of constantly trying to bring Sasuke back with kindness, he might use a more forceful and intimidating approach, just like Yujiro would deal with those who oppose him.
Maybe there's a plot where Naruto is influenced by an external force that makes him act like the Joker. He then starts to target the powerful figures in the ninja world, not to defeat them in a traditional sense, but to expose their weaknesses and make them look foolish, just like the Joker does with Batman. And as he does this, his relationships with everyone around him start to crumble.