A human with a mysterious past, like a former street urchin from Coruscant who has a natural affinity for the Force. This character would start off very naive about the ways of the Sith but quickly learn under Vader's harsh training. Their journey from a nobody to a powerful apprentice could be full of twists and turns.
Maybe Valerie could be the apprentice. She has her own experience with fighting ghosts, so she would already have some skills. But as an apprentice to Danny, she could learn new techniques and ways of dealing with ghosts. Also, the dynamic between her and Danny could be really interesting, as they've had their share of conflicts in the past. It would be cool to see them work together in a more positive way. And there's also the potential for her to learn about Danny's secret identity in a new and different way as his apprentice.
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.
There might be some Imperial officers who play important roles. They assist Darth Vader in his plans and also interact with the secret apprentice. Maybe some other Sith acolytes who are either rivals or potential allies to the apprentice.
Well, one possibility is that Naruto, with his ninja skills and positive attitude, clashes with Darth Vader's dark and authoritarian ways at first. But as time goes on, he might learn some unique combat techniques from Vader while also trying to influence Vader with his own values of friendship and loyalty.
If it was a crossover with the Lord of the Rings, Aragorn could be paired with Darth Vader. Aragorn is a noble and skilled warrior, and his leadership skills would contrast with Vader's tyrannical rule. They could start as enemies, but as they learn more about each other's worlds and the threats they face, they might form an uneasy alliance to defeat a greater evil.
One suitable character could be a healer's daughter. She has grown up seeing the power of natural remedies and has a natural inclination towards magic. She is kind - hearted and intelligent, which would make her a great apprentice for Merlin. Also, a young noble who has been shunned by his family for his strange dreams (which are actually premonitions due to his budding magic) could be an interesting choice. Merlin would see the potential in him and take him as an apprentice.
Naruto's character would experience a significant transformation. He'd be exposed to a whole new level of power and control in Vader's world. His development could go in different directions. He could either become more like Vader, ruthless and power - hungry, which would be a huge deviation from his original self. Or he could use the knowledge he gains to become a stronger defender of what he believes in. He might also learn to be more strategic and less impulsive, as the Star Wars universe demands a different kind of thinking compared to the ninja world he comes from. His relationships would also change, as he'd have to interact with different species and characters in the Star Wars setting, and these new relationships would shape his character further.
A young ninja with a lot of potential but also some major flaws could be a great main character. For example, a ninja who is very powerful but lacks self - control. The sennin could then focus on teaching them not just ninja skills but also self - discipline.
It could be a young, inexperienced mage who has always admired Natsu from afar. Maybe someone with a hidden power that Natsu senses and decides to take under his wing.
Lupin could be a very interesting mentor. He could teach an apprentice about dealing with their own inner demons, as he has his own struggles with being a werewolf. He could also pass on his knowledge of defensive magic and how to use magic in a more practical and street - smart way.