A plot might be that the Hufflepuff girl finds a lost Draco in the Hogwarts corridors late at night. He's lost because he's actually trying to find a way to redeem his family's name in secret. The Hufflepuff girl, with her sense of fairness, decides to help him. They start to form a bond as they search for ways to make amends for the Malfoy family's past wrongs. Another idea is that there's a magical creature that's causing trouble around the school. The Hufflepuff girl has a natural affinity for magical creatures, and Draco, being a Slytherin with a knack for getting things done, join forces with her to deal with it. And for a third, the Hufflepuff girl is entered into a wizarding competition, and Draco, surprisingly, offers to be her mentor because he sees potential in her that others don't.
Another plot could be that Hermione, being the brilliant witch she is, gets sorted into Hufflepuff by mistake (or maybe it's not a mistake). She initially struggles with the idea as she has always identified more with Gryffindor. But as she spends time in Hufflepuff, she realizes that the house values are just as important and noble. She then uses her intelligence to help Hufflepuff gain more recognition in the wizarding community.
Maybe the Hufflepuff male OC is an exceptional flyer, even though Hufflepuff isn't known for Quidditch. He tries out for the team and faces discrimination from some of the other houses at first. But through his hard work and kind nature, he not only makes the team but also helps to bring unity among the different houses in the Quidditch matches.
Well, a plot could involve Draco as a girl being in a love triangle. Maybe she has feelings for Harry, but at the same time, there's a Slytherin boy who has been in love with her for years. This could lead to a lot of drama and conflict within the Slytherin house and also between houses. Also, her family might react differently to her as a girl, perhaps her father has different plans for her than he would for a son, and she has to deal with that.
One plot idea could be that they are forced into an arranged marriage by their families to end the long - standing feud between the pure - bloods and the Muggle - borns. At first, they resist but gradually discover they have more in common than they thought. Another idea is that they meet years after the war, both changed people. They start to work together on a project for the betterment of the wizarding world and fall in love during the process. A third plot could be a time - travel story where Hermione goes back in time and has to marry Draco to prevent a dark future from happening, and in the process, they develop real feelings for each other.
Maybe in the fanfiction, Draco is feeling lonely during Christmas break at Hogwarts as his family is in a bit of turmoil. Hermione notices this and decides to be kind. She invites him to join her and her friends for a Christmas celebration in the Gryffindor common room. At first, Draco is hesitant but then he realizes how much fun it can be to be part of a different kind of 'family' for the holidays.
A great plot could involve a prophecy about the twins. It says that together they can either bring great peace or great destruction to the wizarding world. Some factions want to use them for good, while others for evil. Draco and Harry have to figure out who they can trust and what their true purpose is, all while dealing with the normal Hogwarts drama and the fact that they are twins but were never raised as such.
A plot could involve the repairman being hired to fix something in an old, wizard - friendly establishment where Draco has hidden his pensive. The repairman accidentally activates the pensive and is drawn into Draco's memories. Draco then has to enter the pensive to retrieve the repairman and in the process, they both learn valuable lessons about each other's worlds and themselves. As they journey through the memories, they form an unlikely bond that changes their perspectives on life.
One idea could be that Kagome, being from her own magical world in Inuyasha, somehow gets transported to the Harry Potter universe. Draco initially views her as an oddity but gradually becomes intrigued by her different approach to magic. For example, Kagome might use her spiritual powers in a way that's unheard of in the wizarding world. Another plot could involve them teaming up to solve a mystery that spans both of their worlds, like a dark magic artifact that has connections to both the feudal era of Japan and the wizarding world in England. They could also have a sort of cultural exchange where Kagome shows Draco aspects of her Japanese heritage and he in turn teaches her about pure - blood wizarding traditions.
A really interesting plot could be that Draco's transformation into a girl is part of a bigger magical mystery. She starts to notice strange things happening around Hogwarts that seem related to her change. As she tries to figure out what's going on, she teams up with unlikely allies from different houses. Along the way, she also has to deal with the prejudice and confusion from some of the wizarding community who don't understand or accept her new identity.
One idea could be that it's for a magical disguise. Maybe Draco has to infiltrate a group that only allows female entry, so he dons girl clothes. This could lead to humorous situations like him struggling to walk in a dress or getting the makeup all wrong at first.