One possible reason could be a misunderstanding. Maybe there was a miscommunication about their career plans. For example, if one of them got a solo opportunity but the other thought it was a betrayal of their duo concept. Another reason might be jealousy. If one was getting more attention from fans or the media, it could lead to tension and ultimately a fight.
In the fanfic, it could be a fight over personal space. They might be spending so much time together for work that they start to feel suffocated. Louis could feel that Harry is being too overbearing or vice versa. Additionally, past unresolved issues might resurface. Maybe something that happened in their early days together that was swept under the rug but now, with added stress, it explodes into a fight.
Well, it could be due to creative differences. Suppose they were working on a project together, like writing a song. Louis might have had one vision for the lyrics or the melody, while Harry had a completely different one. Their strong-headedness in sticking to their own ideas could result in a fight. Also, external influences like management interference in their relationship or how they presented themselves publicly could be a cause.
Often, they make up. They realize that their friendship or relationship is more important than whatever they were fighting about. It could be a simple apology scene where they admit their faults and hug it out.
Maybe the fight in the fanfiction was really intense and emotional. It could be that Harry's character was deeply hurt by the words or actions of the Louis fanfiction character. Fanfictions often create extreme situations that can tug at the heartstrings.
It could also be due to jealousy. Suppose Hermione is getting more attention or praise for her academic achievements or magical abilities in the story. Harry, feeling a bit left out or insecure, might lash out at her. For instance, if there's a competition at Hogwarts and Hermione is winning, Harry's pride could get hurt and lead to him shouting at her.
One possible reason could be that Harry did something reckless without consulting Hermione. For example, if he went off on his own to face a dark wizard, Hermione, being the cautious and logical one, would be furious. She values planning and teamwork, and Harry's solo actions might seem to her as endangering himself and others needlessly.
Well, it could be that Harry Potter uses his magic skills like the Patronus charm against Thor's lightning. Maybe Thor mistakes Harry's magic for some new Asgardian sorcery at first. And then they start to fight over some misunderstanding, like a magical artifact that Thor thinks is from Asgard but Harry knows is important for the wizarding world.
One possible plot could be that Harry is traveling and stumbles upon the Circus St. Louis. There, he encounters Lamia, who is a mysterious figure in the circus. Maybe Lamia has some special powers that Harry is intrigued by, and he decides to stay and learn more about her.
One possible reason could be a spell gone wrong. Maybe a prank spell intended for someone else backfired on Harry, causing him to magically transform into wearing a skirt. It could also be part of a dare in the story. His friends might have dared him to wear a skirt for a day as a part of some Gryffindor courage - testing tradition. Another reason could be for a disguise. Harry might be on a secret mission and wearing a skirt could be an unexpected disguise to throw off his enemies.
One possible reason could be differences in their views on magic. Maybe Albus wants to explore a more radical or different approach to magic compared to Harry's traditional views. Another reason might be the pressure Albus feels living in his father's shadow. He could be lashing out in an attempt to assert his own identity.
Jealousy can be a reason. For example, if one friend gets more attention or success than the other, the less fortunate one might get jealous and start a fight.
One possible plot reason could be a misunderstanding over creative differences. For example, in a fanfic, one member might have a strong idea for a new song or performance concept, but the others don't see it the same way at first. This could lead to arguments and a sense of fighting between them. Another reason could be related to external pressures, like excessive media attention or overzealous fans. If the members are constantly being pitted against each other by the media or some fans, it might create a fictional scenario where they start to have real friction among themselves in the fanfic.