One possible plot twist could be that Draco's family objects strongly to the marriage. His pure - blood supremacist parents might see Ginny, a Weasley, as beneath them. They could try to sabotage the relationship, which would create a lot of drama. Maybe they'd spread false rumors about Ginny in the wizarding community.
Well, a plot twist could be that Luna discovers Draco has been involved in some sort of dangerous dark magic deal in the past that he hasn't fully come clean about. This could create a huge rift between them as Luna is a very pure - hearted person. Or perhaps there's a miscommunication spell that makes them believe things about each other that aren't true, like Luna thinking Draco is still a Death Eater at heart when he's actually changed. It would take a lot of effort to clear up this misunderstanding.
Well, perhaps a plot twist could be that the magic binding their marriage is somehow linked to an ancient prophecy. This prophecy states that their union will either save or doom the wizarding world. This adds a whole new layer of tension to their wedding day. Also, there could be a plot twist where Ginny's ex - boyfriend shows up and tries to win her back, creating a love triangle - like drama in the middle of the wedding. Or, a magical object that was thought to be a wedding gift turns out to be a powerful and dangerous relic that starts causing trouble at the wedding.
One interesting plot twist could be that Ginny and Draco's pregnancy is a result of a magical accident. Maybe a spell gone wrong during a battle or an experiment that binds their magical essences together. Another could be that they keep the pregnancy a secret from everyone at first, and as they struggle to come to terms with it, they start to develop unexpected feelings for each other. For example, Draco, who has always been a bit of a snob, realizes Ginny's true strength and kindness through this situation. And Ginny sees a more vulnerable side of Draco that she didn't expect.
If there was such a fanfiction, the plot might involve Draco and Ginny initially being in denial about their feelings for each other. But the pregnancy forces them to confront their relationship. There could be a lot of conflict, like how Draco's pure - blood family might react to him having a child with a 'blood traitor' like Ginny. Ginny, on the other hand, would have to deal with the disappointment of her family and friends who have always seen Draco as an enemy. The story could then be about them trying to overcome these obstacles and build a future together for their unborn child.
It's possible that such a fanfiction exists in the huge world of 'Harry Potter' fanfiction. But it might not be a very common or mainstream idea. In the original series, Draco and Ginny are from opposing sides and have different relationships with other characters. So, a fanfiction with this plot would need to do a lot of work to make the story believable and interesting, perhaps by reimagining the characters' personalities and the overall story arc in a significant way.
One interesting plot twist could be that Draco and Ginny initially resist the arranged marriage but then find common ground in their shared love for a particular magical art, like potions. They start working together secretly on new potion recipes and gradually fall in love. Another twist could be that there is a mystery surrounding the arranged marriage, like it was actually set up by an enemy to cause chaos in the wizarding world. As they dig deeper, they uncover a conspiracy and have to work together to stop it. And a third plot twist might be that Ginny discovers she has a long - lost relative who is related to Draco's family, which changes their perspective on the arranged marriage completely.
A great plot twist could be that in the time travel, they end up in an alternate version of Hogwarts where the roles are reversed. Ginny is in Slytherin and Draco is in Gryffindor. This makes them see each other in a completely different light. They have to deal with the prejudices of their new houses while also trying to find a way back to their own time and original selves.
One possible plot twist could be that while drunk, they accidentally reveal secrets they've been keeping from each other. For example, Ginny might let slip about a small insecurity she has in their relationship that she's been hiding. Another could be that they end up in a part of Hogwarts they've never been to before while drunk and discover something mysterious, like an old hidden room with strange artifacts. Maybe they also get into a bit of trouble with the school authorities when they are found drunk, but this incident actually brings them closer as they face the consequences together.
One popular plot twist could be that they keep their relationship a secret from their former Hogwarts friends at first. Their different backgrounds and the history of enmity between Gryffindor and Slytherin make it a big deal. Another could be that there's a prophecy involved that ties their unborn child to some great destiny in the wizarding world. Maybe the child is predicted to bridge the gap between the pure - bloods and the Muggle - borns, which adds a whole new layer of drama to the story.
A possible plot twist is that Hermione is actually on a secret mission for the Order of the Phoenix when she marries Draco. She's using the marriage as a cover to get closer to some dark wizards Draco has connections with. As they spend more time together in their 'fake' marriage, they start to truly fall for each other, which complicates things for Hermione's mission.