Maybe a story where Sirius Black fakes an illness to get close to Madam Pomfrey because he suspects she has some information about his family. But as he spends more time with her in the hospital wing, he starts to feel guilty for deceiving her. Meanwhile, Madam Pomfrey starts to suspect that Sirius is not as ill as he seems, and their relationship becomes a game of cat - and - mouse, filled with tension and unexpected moments of kindness.
A possible fanfiction could revolve around Madam Pomfrey finding out about Sirius Black's innocence long before others do. She could secretly be helping him while he is on the run. Their relationship in this fic could be full of secrecy and mutual respect. Madam Pomfrey could be providing him with potions and medical advice through a secret network, and Sirius could be protecting her identity from those who would use it against her.
A plot could revolve around Narcissa and Sirius in their Hogwarts days. They could be involved in a mystery within the school, like a series of strange disappearances of students. Since they are both from the Black family, they might have some inside knowledge that helps them solve the mystery, and in the process, form an unexpected bond.
One idea could be a humorous take on Sirius as a baby with his magical abilities already showing in unexpected ways while in diapers. For example, he might accidentally levitate his diaper when he gets excited.
Well, he could be in the hospital because of a curse. While there, he starts to form a bond with a young patient who has no family. Sirius then decides to protect this child and in the process, uncovers a plot against the wizarding world that has some connection to the hospital. Or perhaps Sirius is in a coma and his friends use magic to enter his mind in the hospital. They find out things about him they never knew before.
Well, perhaps there's a fanfiction where Sirius Black is wrongly accused again, but this time Hermione believes in his innocence from the start. She uses her intelligence and resources to prove his innocence while they are on the run from the Ministry. Along the way, they form a deep bond and discover new magical abilities within themselves that they use to clear Sirius' name and also make some changes to the wizarding world's justice system.
In a fanfiction, Sirius could have his hair cut by someone else as a sign of trust. For example, he might let a new ally cut his hair, and during the process, they could have a deep conversation about his past, his hopes for the future, and his relationship with Harry. This haircut then becomes a bonding moment between them.
Perhaps Sirius never dies because he is able to use a powerful time - turning spell. He goes back in time and changes the events that led to his supposed death. He warns himself about the trap at the Ministry, and together they work to expose the real traitors in the wizarding world. This could lead to a whole new series of adventures as they fight against the dark forces that are still lurking.
A possible plot could be a time - travel story. Ginny accidentally travels back in time and meets a young Sirius Black. They team up to change an event in the past that has far - reaching consequences for the wizarding world in Ginny's time. Or perhaps Sirius, after his death, is able to communicate with Ginny in a way similar to how he did with Harry. He gives her advice on dealing with her relationship problems, like her feelings for Harry and how to handle jealousy among friends.
Well, perhaps in a fanfiction, Sirius Black could time - travel back to Hermione's school years. He'd be this mysterious figure who helps her with her studies in the Room of Requirement. Their relationship could develop as he shares his knowledge of the old wizarding ways, and they fall in love while trying to prevent some dark magic from resurfacing.
One plot idea could be that Sirius, who has a connection to Ginny through his friendship with the Weasley family, starts to mentor Ginny in some magical skills. He could share his knowledge of the more dangerous aspects of magic, like dark wizard - fighting techniques, which Ginny is eager to learn. This could lead to a strong bond between them as they train together.