Sasuke is often a popular character in these fanfictions. He might play a role in helping Naruto against Madara or have his own motives during their battle. Kakashi can also be a prominent figure, perhaps using his Sharingan in a crucial moment to assist Naruto. Another popular character could be Hashirama, as his connection to Madara is a key part of the original story and can be further explored in fanfiction.
Maybe an orphan from a non - Uchiha clan who has a special ability that Madara finds interesting. This character would be malleable and eager to learn from Madara, as they have no other real family or guidance. They could bring a fresh perspective to Madara's teachings.
Well, in such a fanfiction, it might start with Naruto being in a situation where he becomes Madara's pet. Maybe at first, Naruto is defiant but as time passes, he could start to understand Madara's motives in some strange way. Madara, on the other hand, might initially see Naruto as just a possession but gradually develop a sense of attachment. It could be a really strange and complex relationship that unfolds as the story progresses.
In this kind of fanfiction, the main antagonist could be a new character created out of the chaos caused by the merge. For example, the merge could disrupt the balance of the ninja world in a way that awakens an ancient evil force that was sealed away long ago. This force would see the merged Naruto - Madara as a target to destroy because they represent a new power that could oppose it.
In a fanfiction where Naruto and Madara are friends, it could completely change the Naruto storyline. Their friendship might start from a mutual understanding of their strong wills. Naruto, with his belief in redemption, could see past Madara's actions. And Madara, who has been alone for so long, might be drawn to Naruto's positive energy.
In these types of fanfictions, the story could potentially focus on how the two characters deal with this unexpected situation. For example, Madara, being a powerful and complex character, might have different reactions compared to Naruto. It could also delve into the social and emotional implications within the Naruto universe if such a thing were to occur. There are likely to be many different interpretations depending on the author's vision.
In a Naruto fanfiction where he has Madara's attitude, he could become more power - hungry. Madara was always seeking power to reshape the world according to his ideals. Naruto might start to view the tailed beasts not as friends but as tools for greater power. He could try to gather more chakra and perhaps even attempt to unlock new forms of power that are more in line with Madara's dark and ambitious nature, which would shock his comrades and enemies alike.
Often, the resemblance could be in terms of the way Naruto stands or moves in these fanfictions. For example, Naruto might adopt a more menacing stance similar to Madara's. Also, his hair could be described in a way that it seems to mimic Madara's wild look, perhaps when he's in the middle of using a powerful jutsu.
In some fanfictions, it could be through a strange and powerful jutsu transfer. Maybe Madara, on the verge of defeat, decides to transfer his Rinnegan power to Naruto for some unforeseen reason, like seeing a new path for the ninja world in Naruto.
In this kind of fanfic, the author may describe Naruto's resemblance to Madara in terms of their auras. Naruto could have an aura that is as intimidating as Madara's. For example, when he enters a room, people might feel the same kind of pressure as they would when Madara was around. And perhaps Naruto starts to have some facial expressions that are similar to Madara's, like a certain smirk or a serious frown.