One idea could be that the street kid Harry has some sort of magic that he doesn't understand and Snape discovers it. Maybe Harry uses his street - smarts to get out of tricky situations in the wizarding world, and Snape is reluctantly impressed.
Perhaps Harry, as a street kid, stumbles upon one of Snape's secret potions experiments. This leads to an unlikely alliance as Snape realizes Harry has a natural talent for potion - making, despite his rough upbringing. And they have to work together to keep the experiment a secret from others in Hogwarts.
A plot could involve Harry being on the run as a street kid and finding refuge in Snape's quarters at Hogwarts. Snape at first wants to turn him in, but as he gets to know Harry's story, he decides to protect him. Along the way, they both learn more about each other's pasts and develop an unexpected bond.
Another idea could be the friendship between the street kid and the well - known Harry Potter characters. Maybe the street kid is initially distrustful of them but gradually learns to trust and rely on them. They could bring a different perspective to the magical world that the other characters haven't considered before.
Well, perhaps in the fanfiction, they are all entered into a magical tournament. Harry, being the young and brave one, Snape with his vast knowledge of magic, and Lucius with his family's resources. At first, they are rivals in the tournament but then realize that there is an outside force trying to manipulate the outcome for evil purposes. So they join forces. Or it could be that a powerful dark magic spell has been cast over Hogwarts, and only the combined magic of Harry, Snape and Lucius can break it. They start off distrustful but as they work together, they form an unlikely alliance.
One idea could be that Harry punches Snape in a moment of extreme frustration after Snape makes yet another snide comment about his father. Then, Harry realizes the gravity of his actions and has to face the consequences within Hogwarts, which could lead to a series of adventures as he tries to make amends while also uncovering some long - hidden secrets about Snape's true motives.
Well, it could start with Harry having to take private lessons from Snape for some special magic he needs to learn. During these lessons, they begin to understand each other's past traumas and find common ground. Maybe there's a magical bond that forms between them accidentally, like a soul - bond, which makes them feel each other's emotions. This could lead to a slow - burning relationship as they figure out how to deal with this new connection. And also, a plot where they are both on a quest to find a lost magical artifact and in the process, their relationship evolves from animosity to love.
Well, perhaps one plot point could be Harry's struggle to find a place to sleep at night. Another might be his encounters with different street gangs and how he manages to avoid getting involved in their bad activities. Maybe he also has a special talent for something, like singing or drawing, which he discovers while living on the streets.
Perhaps in the fanfiction, Snape and Harry are forced to team up to defend Hogwarts against a new, unknown dark force. They have to rely on each other's skills and knowledge, with Snape using his potions expertise and Harry his courage and Gryffindor - like bravado. Along the way, Snape shares some of his own experiences with dark magic and how to combat it, making Harry a more well - rounded wizard.
One interesting plot idea could be that Snape, in raising Harry, teaches him advanced potions from a very young age. Harry becomes a prodigy in potions, much to the surprise of the other Hogwarts students. Another idea is that Snape's strict but fair upbringing makes Harry more reserved and less impulsive, which changes the way he interacts with his friends. He might be more cautious and calculating in his actions, especially when dealing with enemies like Voldemort.
One plot idea could be that Dudley somehow gets involved in the wizarding world due to a magical accident. Snape, initially reluctant, has to keep an eye on him. Meanwhile, Harry is caught in the middle, trying to balance his relationship with Dudley and dealing with Snape's grumpiness. For example, Dudley could accidentally drink a potion meant for someone else and start showing magical abilities, leading to chaos and an unlikely alliance between him and Snape to reverse the effects.
One idea could be that in an alternate universe, Snape manages to save Lily and they both play a big role in Harry's upbringing along with Hermione. Maybe Snape uses his potions expertise and Lily's charm work to create a special protection spell for Harry that Hermione later helps to understand and strengthen. Another plot could be that Lily didn't die but was in hiding, and when Harry enters Hogwarts, Snape has to reconcile his feelings for Lily with his role as a teacher to Harry, while Hermione gets caught in the middle trying to figure out the truth behind their complex relationships.
One plot idea could be that Harry, as a pet in this fanfiction universe, has some unique magical abilities that only Snape can understand and help him develop. For example, Harry might be able to communicate with magical creatures in a special way. Another idea is that Snape takes Harry under his wing as a pet to protect him from the real threats in the wizarding world that others don't see. Maybe there's a prophecy related to Harry's 'pet' status that Snape is trying to figure out.