Perhaps Snape would force them to work together on a task as punishment. This could be something like cleaning the Potions classroom without magic or helping in the Forbidden Forest. During this time, they might start to understand each other better. Harry could see that Draco isn't just a spoiled brat all the time, and Draco could see that Harry has more depth than he initially thought.
Well, it could be that in the 'Harry and Draco apprentice with Snape' fanfiction, they end up learning a lot about the Dark Arts from Snape, not in an evil way but in a way to defend against them. Harry would be skeptical at first but then realize the importance. Draco might be more eager as he has some knowledge of the Dark Arts from his family. Snape could also teach them how to brew complex potions that are useful in both dueling and healing. There could be some rivalry between Harry and Draco in terms of who can master the skills faster, but also moments of cooperation when they face difficult tasks.
One possibility is that Harry would be extremely hurt and angry. He might immediately confront Ginny about it. He could cut off all ties with her and distance himself from their mutual friends as well, feeling betrayed not only by Ginny but also by the false image he had of their relationship.
One possibility is that Sirius could be initially shocked. But then, being the understanding person he is, he might give them his blessing. After all, he has seen how Harry has grown and Ginny is a great girl.
If Snape adopts Harry and Draco, it could change the whole dynamic of Hogwarts. Snape would have to ensure that both boys are getting proper magical education while also taking care of their emotional well - being. Harry might start to see Snape as more than just a teacher who was always tough on him. Draco would be forced to interact with Harry in a more positive way. There could be some really heartwarming moments as Snape tries to show his affection for the two boys in his own, rather gruff way. And perhaps they could all form a strong, if unconventional, family unit.
Snape might also keep what he saw to himself at first. Instead of immediately confronting them, he could choose to observe them further. He might be curious about what they were really up to and use his skills as a spy to find out more. This way, he could gather more information before deciding on the best course of action, whether it be punishment or something else entirely.
One possibility is that Snape would be extremely strict with them at first. Given his past relationship with Harry especially, he might struggle to show affection openly. But over time, he could come to understand the trio better. Harry would likely be the most resistant to Snape's parenting at the start, but as Snape showed his genuine care, Harry might warm up. Hermione would probably be eager to learn from Snape, seeing his vast knowledge. Ron, on the other hand, might find Snape's gloomy demeanor a bit off - putting, but with Hermione and Harry's influence, he'd also adapt.
Well, one possibility is that Harry would be completely shocked. He might initially think Draco is playing some sort of cruel joke on him. After all, they've been rivals for so long. But then, he could start to consider it seriously. Maybe he realizes that this could be a chance to bridge the gap between them. He might accept, which would cause a huge stir among their friends and classmates.
Well, if Draco gives Harry a lust potion in fanfiction, it could lead to a lot of chaos. Harry might start having unexpected feelings towards Draco or others around him. His normal behavior would be disrupted as the potion takes over his emotions. He could struggle to control his actions and thoughts, which would create a very interesting dynamic in the story.
In such a fanfiction, perhaps Snape catches Hermione breaking a minor school rule like sneaking into the restricted section of the library. He might give her a stern warning or a detention as a result.
Maybe they were in the middle of a surprise for her. For example, they could be making a handmade gift but she caught them before they were done. Then she would probably feel bad for interrupting and join in to help them finish. Another possibility is that they were fighting, and she'd have to step in to sort out their differences and teach them about getting along.