One common theme is the power dynamic. Ozai is a powerful figure in the Fire Nation, and how he wields that power over his baby son, Zuko, is often explored. For example, in many fanfictions, he starts to instill in Zuko the importance of strength and power from a very early age.
There's also 'Baby Zuko's First Years'. In this fanfiction, it focuses on the early days of Zuko's life with Ozai in the Fire Nation. It explores the different ways Ozai might have interacted with his son during those formative years, like his attempts to mold Zuko into a powerful heir from a very young age.
In the fanfiction, the baby might have a unique appearance. It could have Katara's blue eyes and Zuko's dark hair. Personality - wise, it could be a blend of their traits. Zuko's determination and Katara's compassion. Maybe the baby is also very empathetic, able to sense the emotions of others around it, which is a trait that could come from both of their sensitive natures.
One interesting zuko and katara baby fanfiction could be about their journey of raising a child in a world that is still recovering from war. The story might focus on how they teach their child about the different cultures that they come from.
Love and family would be a major theme. Zuko and Mai's love for each other is shown through their joint responsibility of raising their child. Another theme could be growth. They both grow as individuals as they learn to be parents.
Perhaps the fanfiction delves into the baby's unique abilities or characteristics. Since Zuko has a connection to the Fire Nation and Mai is a skilled fighter, the baby could inherit some extraordinary powers. It could show how they train the baby to control these powers while also giving it a normal childhood.
He would be super excited. Zuko would probably be right there on the floor with Izumi, coaxing her to take those first steps. He might hold out a small, shiny object from the Fire Nation as an incentive.
Their relationship would likely become more intimate and complex. They would have to rely on each other more, sharing a bond that goes beyond their previous friendship or alliance. Zuko would probably become more protective of Katara, and Katara would trust Zuko with her vulnerability during pregnancy.
In such a fanfiction, the story could be about the challenges of raising a child in a world that's still recovering from war. Their baby might be a symbol of hope for the future. Zuko and Katara would have to combine their different cultures, Fire Nation and Water Tribe, in raising the child. Maybe the baby has unique bending abilities that are a combination of fire and water, leading to some interesting plotlines as they try to help the child understand and control their powers.
I really like the one where Zuko and Katara's baby has an adventure in the spirit world. It's a great story as it shows the baby's connection to the spiritual side of the Avatar world, and how Zuko and Katara have to figure out how to get their baby back from the spirit world. It has a lot of elements of mystery and discovery.