One possible plot could be that Aku somehow ends up in the Naruto universe. Naruto, being a fan, is initially excited but then realizes that Aku's presence is causing chaos. So, Naruto has to find a way to either send Aku back or find a way to co - exist with Aku without letting Aku's evil influence overtake the ninja villages. He might try to reform Aku using his own positive attitude and the power of friendship, which is a common theme in Naruto.
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.
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.
Since Naruto has the Nine - Tails' chakra, which is a powerful and primal energy, and Aku has his own otherworldly and malevolent energy, they could combine these energies in a last - ditch effort to defeat an ultimate enemy. This combination could create a completely new form for Naruto, one that has the strength and ferocity of the Nine - Tails along with Aku's dark and mysterious powers. It would be a visually stunning and very powerful transformation that could turn the tide of a great battle.
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.
Aku could be a storyteller. Maybe it's a person's name.
Well, a plot could revolve around Aku trying to keep his pregnancy a secret from Samurai Jack. He might be worried that Jack would use this new situation to his advantage. And then there could be a sub - plot about Aku having strange cravings that lead him to unexpected places in the world of the fanfiction, causing chaos in different ways.
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.
Well, the plot could be that Jenny is a time - traveler who accidentally lands in the Naruto universe. She has unique knowledge from her own time which Naruto finds useful in his battles. They form a quick bond as they try to figure out how to send her back while also dealing with the various threats in the ninja world.
It could be about Naruto obtaining kami - like powers. Maybe he discovers he has a connection to the kami and has to learn how to control these new powers to save the Hidden Leaf Village from a great threat. Or perhaps he is chosen by the kami to be a sort of bridge between the human and divine worlds in the Naruto universe.
In a 'Naruto is Valkorion' fanfiction, the plot could start with Valkorion sensing a strange new energy, which turns out to be Naruto. Naruto, not fully understanding the 'Star Wars' universe, could start causing disruptions. As he comes to understand Valkorion's role, he might decide to help Valkorion in his fight against other dark forces, but only if Valkorion agrees to follow Naruto's more moral code. This would lead to a series of adventures where Naruto tries to change the 'Star Wars' universe for the better while being in Valkorion's position.