In the 'Luke joins the Empire fanfiction', it could start with Luke being captured by the Empire. Instead of being killed, he is given an offer he can't refuse. The Empire shows him a vision of a more 'orderly' galaxy under their rule. Luke, thinking he can use this opportunity to learn more about the Sith and how to defeat them, decides to join. He then has to navigate the complex politics and power struggles within the Empire while trying to keep his true intentions hidden from those who would use his power for evil.
One possible plot could be that Luke is disillusioned with the Rebellion after some major setbacks. Maybe he discovers some secrets about the Rebellion that make him question their motives. So, he decides to join the Empire in the hope of bringing about change from within. He might start off by using his Jedi skills to gain favor among the Imperial ranks.
In the fanfiction, Luke could be influenced by his family ties to the dark side. If he discovers some hidden connection to Vader or Palpatine that he didn't know before, it might make him question his place on the light side. He could think that joining the dark side is a way to understand his true heritage better and gain more power to protect those he loves in a different way than the Jedi would allow.
Another possibility is a group of Imperial scientists who are conducting unethical experiments with the Force. They see Luke as a prime specimen and try to control him. They would be the main antagonists as they try to use Luke for their own immoral purposes rather than allowing him to pursue his own agenda within the Empire.
In the 'Luke Joins the Academy Fanfiction', it's possible that Luke discovers a hidden talent within himself while at the academy. This could lead to him getting special attention from the teachers or being selected for a unique project. He may also develop a rivalry with another student which adds drama to the story.
Well, perhaps they bring about a new era of peace and justice. They might use their combined skills and knowledge to reform the Empire's infrastructure, focusing on bettering the lives of the citizens across the galaxy.
In a fanfiction where Naruto joins the Akatsuki, there could be a lot of interesting character interactions. He would be in close quarters with villains like Sasori or Hidan. Naruto might try to learn more about their pasts and what led them to become members of the Akatsuki. This could also cause a rift in his relationships with his old friends in Konoha. They might see him as a traitor, while Naruto is actually trying to bring about change in the Akatsuki for the greater good.
In this type of fanfiction, it might also be that Naruto joins Orochimaru to spy on him. The Hidden Leaf Village realizes they need to know Orochimaru's plans from the inside. Naruto, being the brave and somewhat reckless one, volunteers for the mission. He endures Orochimaru's experiments and teachings while secretly sending information back to the village. Eventually, when the time is right, he betrays Orochimaru and uses the knowledge he gained against him.
If Luke joined the Empire in a fanfic, it would be a complete deviation from his original path. He might use his Force abilities to rise quickly within the Empire's ranks. However, his friends like Han and Leia would likely become his enemies, leading to intense and tragic confrontations.
Well, perhaps in this fanfiction, there's a big misunderstanding. Harry might think that by infiltrating the Death Eaters as one of them, he can actually bring them down from the inside. So he pretends to join them, but things get out of hand as he has to constantly prove his loyalty to the dark side, which is really difficult for him.
One plot could be that Naruto is captured by the Sound Village. Instead of being treated as an enemy, they try to convert him. They show him their training methods and how they are building a strong village. Naruto, being the curious and empathetic person he is, starts to understand their motives. He begins to think that by joining them, he can bring about change from within. So, he decides to stay and become part of the Sound Village, while still holding onto some of his Konoha values.
One possible plot could be that Merlin, in his quest to understand the magic that Morgause wields, decides to join her. Maybe he hopes to learn more about his own powers and their origins. Along the way, he discovers secrets about Camelot and his own destiny that he never expected.