He could be in Slytherin. His cunning and ability to manipulate situations in the Naruto series could be seen as Slytherin traits. He was always thinking several steps ahead, just like many Slytherins are known for their strategic minds.
Well, he could be a foreign exchange student of sorts from a hidden land of ninjas. His skills would make him stand out immediately. He might befriend Harry and help him train in a different way of combat, using his Sharingan to analyze the weaknesses of their enemies like Death Eaters.
She might also be a Ravenclaw. Sakura is very intelligent and a quick learner. In the Naruto world, she studied hard to become a skilled medical ninja. At Hogwarts, she would thrive in an environment that values knowledge and wisdom, using her intelligence to solve problems and come up with new magical theories or techniques.
Joker could be a Slytherin. He's very resourceful and has a certain cunning about him, which are Slytherin traits. He's able to strategize well in battles, much like how Slytherins are known for their ambition and ability to achieve their goals through different means.
She could fit into Gryffindor. Just like the Gryffindors, she might be brave and daring. Her shape - shifting abilities could be used to show great courage, like sneaking into a Death Eater's lair. Or she could be in Ravenclaw. Kitsunes are often depicted as very intelligent and wise in their own mythology. So at Hogwarts, she would thrive in Ravenclaw with all the knowledge - seeking students.
Naruto might also be a good fit for Hufflepuff. He has a strong sense of loyalty and is always there for his friends. He works hard to achieve his goals, which are traits of Hufflepuff house as well. In the Hogwarts environment, he would show that Hufflepuffs can be as powerful as any other house with his ninja skills.
Sasuke could be a foreign exchange student of sorts. His Sharingan might be seen as a very rare and powerful magical ability. He would likely be very good at Defense Against the Dark Arts due to his combat skills.
Maya could be a Slytherin. She's often a bit of a rebel and is very resourceful. Slytherins are known for their cunning and ability to get what they want, and Maya has shown that she can be quite sly when she needs to be in order to protect herself or her friends.
Sure. There are often crossovers in fanfiction. Writers like to combine different beloved fictional characters. For the 'Harry Potter is Itachi Uchiha' idea, it could be really interesting. For example, Itachi's Sharingan abilities could be compared or integrated with magic in the Harry Potter universe. It might be a bit of a stretch in terms of the two very different settings, but that's the beauty of fanfiction. You can find such fanfictions on websites like Archive of Our Own or FanFiction.net if they exist.
The relationships between the houses can also be inspiring. There's always a bit of rivalry between Gryffindor and Slytherin. You could write a fanfic where students from these two houses have to work together on a project and they learn to see past their differences. And for Ravenclaw, their intelligence can be used to create a story where a Ravenclaw uses their smarts to solve a mystery that has been plaguing Hogwarts for years.
Madara's Sharingan would be a very unique ability in the Harry Potter world. It could be used for things like detecting lies, seeing through invisibility spells that are not as advanced as the Sharingan's capabilities, and predicting an opponent's moves in duels. His ability to use fire - based jutsu could be seen as a form of very powerful and different magic. Also, his physical combat skills would make him a formidable opponent in a world where most rely on wands for combat.