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.
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.
The story follows Samurai Jack as he travels through different time periods to battle various foes. He uses his swordsmanship skills and his wits to overcome challenges and right wrongs.
The main character in Samurai Jack Battle Through Time story is, of course, Samurai Jack himself. He is a samurai from the past who has been thrust into different time periods. Aku is another major character, being the source of all the chaos and Jack's archenemy. Then there are various supporting characters that Jack meets in different time zones. Some are ordinary people who look up to Jack for protection, and others are strange creatures or warriors. Each character, whether major or minor, plays a role in shaping Jack's journey through time and his battles against the forces of evil.
One common theme is the struggle between good and evil, as Jack represents good and Aku represents evil. Another is the concept of fate, as their battles seem pre - ordained.
One great Samurai Jack fanfiction story is 'The Lost Years of Jack'. It delves into what Jack might have been through during his time away from his home. It's really interesting as it shows his struggles and how he managed to keep his spirit alive in the face of so many challenges.
It depends. Some consider them canon if they fit seamlessly into the established Samurai Jack universe and don't contradict the main storylines. Others might have different opinions.