One challenge could be the reaction from Harry's friends. Hermione and Ron might be very skeptical of Morphen Gaunt due to her family name or her past actions. They could try to convince Harry that it's a bad idea, creating tension in their friendships.
The wizarding society at large might not accept their union. Given Morphen Gaunt's potential connection to the dark arts or her family's reputation, there could be a lot of prejudice. This could lead to them facing social isolation and having to fight for their right to be together in the wizarding world.
One possible plot could be that they meet in a very unexpected way. Maybe Morphen Gaunt is on a mission related to the dark arts and Harry, being the hero he is, tries to stop her. But during their interactions, they discover a deep connection that transcends their initial enmity and eventually fall in love and get married.
Yes, there are some out there. You can start by looking on fanfiction platforms like Archive of Our Own or FanFiction.net. However, keep in mind that the quality can vary greatly. Some might focus on exploring an alternate universe where this strange pairing occurs, delving into how their different backgrounds and magic would interact in a relationship.
It might involve a lot of world - building around the relationship. Since Merope Gaunt is from an old and rather dark wizarding family, there could be elements of her family's influence on their relationship. And for Harry, his more modern - day values might clash with the traditional ways of the Gaunt family.
Cultural differences would be a big one. For example, in terms of family values. In Japanese culture, family often has a more collective approach compared to the more individual - centered approach in the wizarding world Harry is used to. Also, magical traditions might clash. British wizarding traditions like the sorting hat might be very different from Japanese magical traditions that the girl is used to.
The cultural differences between the wizarding world and the DC universe would also be a problem. They have different ways of doing things, different social norms. Harry is used to a world where magic is the norm, and a DC villain might not understand or respect that. And vice versa, the villain's world of high - tech and superheroes might be very foreign to Harry.
I think Merope Gaunt is also very fascinating in fanfiction. Her tragic love story with Tom Riddle Sr. is often explored in more depth. Fanfic writers might expand on her use of love potion and the consequences it had on her life and the life of her son, Voldemort, which gives a new perspective on the origin of the Dark Lord.
One challenge could be cultural differences. Harry is from a world where magic is more about spells and potions, while Zatanna's magic is more about incantations and showmanship. Another challenge might be the acceptance of their relationship by their respective communities. Some in the wizarding world might think Zatanna's magic is too different and unorthodox, and some in Zatanna's world might not understand the ways of the wizarding world. Also, they might face villains who target them because of their combined power and the threat they pose to the status quo.
In some versions of this fanfiction, the Vegas part could be a parallel dimension that Harry accidentally stumbles into. There, he discovers a different set of rules and meets a person who is his soulmate in that dimension. Since he has always been a bit of a rule - breaker and a hero, he decides to marry this person despite the differences. It could also be that the story is a comical take on Harry's life, where he goes to Vegas with Ron and Hermione for a lark, and things go hilariously wrong and right, resulting in him getting married.
One possible theme is the clash of cultures. Harry comes from a world of magic hidden from muggles, and the princess from a more traditional monarchy - based world. Their union would involve dealing with the differences in their upbringing, values, and social norms.
For Harry, he might become more open - minded and adaptable. Growing up in the wizarding world, marrying Hana would expose him to a whole new set of values and cultures. He could develop a greater sense of patience and understanding. For Hana, she might become more confident and adventurous. Being with Harry and getting involved in the wizarding world would likely push her out of her comfort zone. She could learn to be more assertive in the face of the magical and often dangerous situations in Harry's world.