I'm not sure who Aku specifically is. Aku could be a person with a great imagination who tells all kinds of stories, like adventure stories, fairy tales or even true - life stories.
It could be someone from the Naruto universe who doesn't like Naruto's newfound fascination with Aku. For example, Danzo might see Naruto's interest in Aku as a threat to the stability of the village and try to stop Naruto from further exploring Aku - related things. So, Danzo could be the main antagonist in this case.
The character of Aku could be developed in a 'pregnant Aku in Samurai Jack fanfiction' by exploring how he interacts with the world around him differently. He may become more reclusive as he doesn't want others to see his 'weak' state. Or he could become more aggressive in trying to protect his pregnancy, which would be a new aspect of his character. Also, his relationship with his own power might change. Maybe he has to find new ways to use his magic that don't harm the unborn, which would force him to grow and adapt in ways he hasn't before.
Yes, the Cinderella - type story, where there is a hero or heroine rising from difficult circumstances, is quite popular. It often contains elements of hope, transformation, and the triumph of good over bad. Many readers are attracted to these kinds of stories as they can be inspiring and relatable.
The key features are quite interesting. The hero is often an outcast or in a low - status position at the start. They experience unfair treatment or a lack of opportunities. However, they possess certain inner qualities like kindness, courage, or intelligence. As the story progresses, they encounter obstacles that test these qualities. There's also a significant event or series of events that propel them into a new, more positive situation. This could be falling in love with someone who sees their true worth, or achieving something great that changes how they are perceived in their world.
One idea could be a crossover where Aku accidentally opens a portal to the Naruto universe. Naruto, being the curious and brave ninja he is, decides to explore Aku's world. They could start off as enemies, but gradually come to understand each other's motives and end up teaming up against a greater evil that threatens both of their worlds.