One common theme is the theme of mentorship. Sirius often takes on a mentorship role when he catches them. He uses his knowledge of the wizarding world, especially the darker aspects, to guide Harry and Hermione. Another theme is friendship. Their friendship is tested and strengthened when Sirius catches them in some kind of 'forbidden' activity. It shows how they support each other through difficult situations.
The theme of discovery is also quite common. When Sirius catches them, they might be in the middle of discovering something new, like a hidden spell or a secret passage. And Sirius becomes part of that discovery journey. Additionally, the theme of family can be present. Sirius, being like a family member to Harry, brings in the family aspect. He might protect them like family or help them understand their own family histories better.
A theme of trust can be found in such fanfictions. Sirius has to decide whether to trust Harry and Hermione's motives when he catches them. And they in turn have to trust that Sirius will not overreact or punish them severely. This exploration of trust within the context of the wizarding world and their relationships makes for an interesting and often recurring theme.
One possible plot idea could be that Sirius catches Harry and Hermione in the middle of a secret plan to save a fellow student from a dark magic threat. Sirius, initially thinking they're up to something dangerous, then realizes their noble intentions and decides to help them. Another idea is that Sirius catches them while they are exploring a hidden part of Hogwarts that is related to an old mystery about his family. He then shares his knowledge about it with them, leading to an exciting adventure.
A lot of these fanfictions explore the idea of forbidden love. Hermione and Sirius come from different generations in the original series, so when he's portrayed as dark, it adds an extra layer of taboo to their relationship. Also, mystery and adventure are common. They might be on a quest together, with Sirius' dark side influencing the journey in various ways.
One common theme could be the exploration of forbidden love. Since Sirius is much older and in a different generation than Hermione in the original series, the idea of their relationship goes against the norms. Another theme might be the struggle with one's emotions. Hermione, being a rational character, lusting for Sirius could lead to her internal conflict between her logical side and her new - found emotions.
One common theme is time - often Hermione travels back in time to meet young Sirius. Another theme is friendship. Since they are from different generations in the wizarding world, their friendship is an interesting exploration. For example, they might share knowledge about magic that the other doesn't know.
Another theme is family. Since Harry lacks a proper family, Sirius becomes like family to him. Fanfictions explore how they create a family - like bond in the absence of Harry's real family. It can be really emotional.
There is a fanfiction titled 'Under Sirius' Watch'. In it, Sirius catches Harry and Draco sneaking around the castle at night. This leads to a series of events where Sirius has to decide whether to report them or try to understand what's really going on between the two. The story delves deep into the characters' emotions and the complex relationships within the Hogwarts world.
One common theme is time - bending. Since they are from different generations, often the stories play with time travel or alternate timelines to make their relationship possible. Another theme could be the clash and then the melding of their personalities.
The theme of mentorship is also present. Sirius, with his knowledge of the wizarding world and magic, becomes a sort of mentor to Hermione. He guides her through difficult situations and helps her grow in her magical abilities. And there's the theme of loyalty. Sirius is extremely loyal to Hermione, just as he was to his friends in the past, and this loyalty drives his actions to protect her.
One common theme is the clash of different generations. Sirius is from an older generation compared to Hermione, so there are often differences in values and beliefs that create interesting conflicts.
One common theme is redemption. Sirius has had a troubled past, and Hermione could be seen as the one to help him fully redeem himself. Another theme is the power of love across different generations. Since they are from different age groups in the original series, the fanfictions might explore how love can bridge that gap.