Yes, there are some. You can find them on various fanfiction websites. Just search for 'batman married' on platforms like Archive of Our Own or FanFiction.net.
Well, the theme of identity is quite common. Batman is known as a dark and brooding vigilante. But when he's married, he has to figure out how to be a husband as well. There's also the theme of trust. His spouse has to trust him with his double life, and he has to trust her not to expose his secrets. And of course, the theme of love conquering all, even in the dark and dangerous world of Gotham.
Definitely. One interesting aspect in some of these fanfictions is how they handle the power dynamics between Batman and Zatanna. Since Zatanna has magic powers and Batman is more of a detective with gadgets. In a married relationship, these differences can lead to really unique storylines. Also, some fanfictions explore how their marriage could potentially change the future of Gotham and the entire DC universe.
One common theme is the struggle between their public and private lives. Batman has his duties in Gotham, and Zatanna has her own magical responsibilities. Another theme is how they deal with secrets, as both characters are known to have their own hidden aspects. Their marriage might put a strain on keeping those secrets.
It would probably be a very secretive event. Since Batman has so many enemies, he would want to keep the location and time of the wedding under wraps. Only his closest allies would be invited.
Some fanfictions might even pair Batman with an original character. This allows for a lot of creative freedom as the writer can design a character specifically tailored to complement Batman and create a unique love story leading to marriage.
The Joker would be furious. He would see Harley's marriage to Batman as a complete betrayal. He might go on a rampage in Gotham, trying to destroy everything that Batman and Harley hold dear. Robin would be very confused at first. He has always seen Harley as a villain, and the idea of her being Batman's wife would be hard to accept. He would need time to come to terms with it.
The Joker could be a great antagonist. He might be jealous of Batman's new relationship and see it as an opportunity to cause chaos. He could try to drive a wedge between Batman and Poison Ivy, using his mind games and unpredictable nature to create misunderstandings and conflicts within their marriage.
Well, in some fanfictions, their married life might be a bit of a struggle. Batman's brooding nature could clash with Wonder Woman's more positive and idealistic outlook. However, they would also learn from each other. For example, Batman could become more open - minded under Wonder Woman's influence, and she could learn about the darker side of humanity from him. They would support each other in protecting the world, with Batman handling the more stealthy and detective - like operations while Wonder Woman took on the more upfront battles.
Another plot could be that they have a child who has a unique combination of their powers. This child becomes a target for those who want to use its powers for evil or those who fear its potential. Batman and Poison Ivy then have to protect their family while also dealing with the challenges of being a married couple with very different backgrounds and moral compasses.