One interesting idea could be exploring Eren's potential even as a baby in the context of the Attack on Titan world. Maybe showing how his early experiences, even as a baby, might shape his future determination against the Titans.
Perhaps in the 'attack on titan baby eren fanfic', the author could play around with the idea of Eren having some sort of hidden power or intuition even as a baby. This could be something that is not fully realized until he grows up, but little hints and events in his babyhood could foreshadow it. It could also show how the world around him, the threat of Titans, starts to influence him at a very young age, like in a more subconscious way that affects his actions and decisions later in life.
Well, in such a fanfic, it might be interesting to see how the other characters interact with baby Eren. For example, how Mikasa or Armin might have a different kind of bond with him right from his infancy, which could be a deviation from the original story and add a new layer of depth to their relationships.
One idea could be exploring Eren's family life as a baby. Maybe showing how his parents interacted with him in a more detailed way, like his mother singing lullabies. Another could be a story where baby Eren has some sort of premonition about the future in his dreams, which is a very unique take on his character.
One idea could be exploring Dark Eren's internal struggle in more depth. Maybe he has to make really tough choices between his friends and his new, darker goals. Another could be a scenario where Dark Eren tries to recruit others to his side, and how they react to his changed personality.
One possible fanfic plot could be that Eren has been planning this for a long time. He might gather intelligence about the Colossal Titan's weaknesses. Then, in a fierce battle, he manages to get close enough to deliver a fatal blow. This could be a very emotional moment for him as well, considering the history between them.
A theme that often comes up is destiny. Fans like to write about how even as a baby, Eren is already on a path towards his future as a Titan - shifter and a hero. It's about how his early days might be subtly guiding him towards that fate. For example, he might show signs of great strength or determination even as a tiny baby. And also, protection is a theme. His family and those around him are trying to protect him from the harsh reality of the world outside the walls, which is a big part of many baby Eren fanfictions.
A great idea for an 'Attack on Titan' permanent titan fanfic would be to focus on the relationship between a permanent titan and a human. It could be a story of an unlikely friendship or a situation where the human is trying to study the titan to gain some sort of advantage in the fight against the other titans. The fanfic could also delve into the emotional and psychological aspects of the titan, if it has any remnants of its former human self, and how it copes with its existence.
One idea could be that Hanji discovers a new side of Eren during a mission outside the walls. Maybe Eren has a unique way of dealing with the Titans that Hanji finds fascinating, and this leads to a deeper bond between them as they study his abilities together.
One interesting 'Baby Attack on Titan Fanfic' could be about a baby who has some sort of special connection to the Titans. Maybe the baby is found in a Titan - infested area and has an uncanny ability to calm the Titans down. This would be a really unique take on the Attack on Titan universe as it adds a completely different element to the otherwise very dark and violent world of the series.
Obviously, Eren as a baby is the central character. But we can also expect to see his family members like his father, Grisha. His mother, Carla, would also be an important presence as she plays a significant role in Eren's early life.
The plot could involve a conflict within the group of titan shifters because of the tenth titan. Some might see it as a threat, while others believe it's the solution to end the war. The tenth titan's power could be something that disrupts the balance between the different factions. For example, it could have the ability to nullify the powers of other titans, which would make it a highly sought - after and dangerous power.
Another interesting concept could be a story where a group of characters from 'Attack on Titan' find themselves in a world full of Kaiju. They have to adapt their combat skills and use their knowledge of Titans to survive against these giant beasts. They might discover new ways to fight and new alliances along the way.