Well, a plot could involve a student who is an artist. The Room of Requirement becomes a studio filled with magical art supplies. As they create, their art comes to life and starts to tell stories about the founders of Hogwarts. Or, it could be that the room becomes a library with books that can't be found anywhere else in Hogwarts. These books contain secrets about ancient spells that could change the balance of power in the wizarding world. Also, perhaps the room turns into a sort of animal sanctuary where magical creatures from all over the world come to be healed and protected.
One idea could be that a group of students discover a hidden section within the Room of Requirement that has a time - travel portal. They then have to decide whether to use it to change certain events in the wizarding world's history. Another could be that the Room of Requirement creates a magical garden full of plants that can talk and offer wisdom. And a third idea might be that the room turns into a training ground for a new and dangerous form of magic that the students have to master to save Hogwarts from a new threat.
A plot could be that Harry and Hermione are looking for a way to bring back some of the lost memories of the students who were affected by a powerful forgetfulness charm during a battle. In the Room of Requirement, they find a magical device that can restore memories, but they have to go on a quest within the room to find the power source to activate it. Another idea is that they use the room to train for a magical tournament that's different from the Triwizard Tournament. They face all kinds of magical challenges created by the room itself, and in the process, they grow closer as friends and develop their magical skills even further.
One idea could be a story about the Gryffindor Quidditch team in the locker room before a big match. Maybe there's some friendly banter among the players, like Harry Potter trying to boost the team's morale with a humorous speech. Another could be a story of a new student accidentally stumbling into the Slytherin locker room and the reactions of the Slytherin students.
One interesting plotline could be about a character using the Room of Requirement to hide a powerful and dangerous magical artifact that was thought to be lost. The protagonist has to keep it a secret from both the good and bad wizards while trying to figure out what to do with it. Another could be students using the room to create a secret study group for a very advanced and restricted area of magic, and they have to avoid getting caught by the professors. And a third plotline might be about a character who accidentally discovers a hidden passage in the Room of Requirement that leads to an unknown part of Hogwarts filled with ancient magic and mysteries.
Another scenario is that the room transforms into a time - traveling portal. Harry and Ginny accidentally step into it and end up in a different era of Hogwarts. They have to figure out how to get back while also dealing with the different magical rules and customs of that time. This adventure tests their relationship and their knowledge of magic.
A possible plot for a Harry Potter shower room fanfiction could be that the shower room is haunted by the ghost of a former student who was wronged in that very place. Harry, being the brave one, decides to communicate with the ghost and find out what happened to help it move on. Another idea is that the shower room's water has some special magical properties that start affecting the students' magical abilities in unexpected ways. For example, it makes Neville suddenly able to perform advanced herbology - related spells. And a third idea is that the Marauders once hid a prank - related map in the shower room that Harry discovers, and it leads him on a wild adventure around Hogwarts.
One possible plot could be that Harry and Ginny discover a hidden part of the Room of Requirement. Maybe they are looking for something specific, like a powerful magical artifact left behind by an old wizard. As they explore, they face some magical challenges and traps. Ginny's quick thinking and Harry's experience help them overcome these obstacles. In the process, their relationship deepens as they rely on each other for support.
One idea could be Harry Potter arriving in Skyrim and using his magic to combat the dragons. Maybe he teams up with the local mages and they learn from each other's magical techniques.
One idea could be exploring what would happen if a new, mysterious student joined Hogwarts during the Triwizard Tournament. This student could have a hidden agenda related to the Dark Arts and start influencing the events of the tournament in unexpected ways.
One interesting plot idea could be Harry's return to Hogwarts as a teacher. He could pass on his unique experiences and knowledge to the new generation of students.
One idea could be a dragon that forms a bond with Harry and helps him in his battles against Voldemort. Maybe the dragon has some special powers that are crucial for Harry to win.