There might be a fanfiction where the Dursleys are forced to enter the wizarding world due to some magical accident. This could lead to all sorts of comical and tense situations as they struggle to adapt to a world they have always despised. For example, Vernon Dursley having to deal with talking portraits or flying broomsticks.
One interesting fanfiction could be about Vernon Dursley having to face a magical threat in the Muggle world on his own. He might have to rely on some of the little knowledge he has about the wizarding world through Harry. Another could be a story where Vernon and Harry are forced to work together during a crisis that affects both the Muggle and wizarding communities, changing their relationship completely. There could also be a fanfiction exploring Vernon's past and how it might have influenced his treatment of Harry, and then how things could have been different if certain events in his past were changed.
One interesting fanfiction could be about Vernon Dursley's perspective during the time when Harry first received his Hogwarts letter. It might explore his extreme reactions and the inner turmoil he felt at the thought of magic being real. Another could focus on a situation where Vernon has to interact with the wizarding world in an unexpected way, like when he accidentally stumbles into Diagon Alley.
One interesting fanfiction could be about Dudley having a change of heart and secretly helping Harry in the wizarding world. Maybe he discovers some magic ability of his own, which is a total twist from the original story.
There are fanfictions where Petunia has a change of heart towards Harry. For example, she realizes the error of her ways after seeing how much danger Harry is constantly in at Hogwarts. She then tries to make amends by secretly helping him, like sending him care packages with useful Muggle items that can be adapted for magical use.
There could be a fanfiction where Petunia Dursley discovers some hidden magic within herself and this somehow links her more closely to Harry. In this scenario, the story could take on a whole new dimension. But as for a particular 'Harry Potter and Petunia Dursley lemon fanfiction', it's hard to point out one without really searching through various fanfiction sites. Also, remember that lemon content often implies sexual undertones which may not be appropriate for everyone.
One popular 'Harry Potter Dursley' fanfiction might be 'The Dursleys' New Perspective'. It delves into how the Dursleys' lives are changed in unexpected ways. Another could be 'Dursley Encounters', which explores their interactions with the wizarding world in a unique manner. There's also 'The Secret of the Dursleys' that reveals hidden aspects of their family.
One great 'Harry Potter Dursley abuse' fanfiction is 'The Boy Who Lived Again'. It delves deep into how Harry copes with the abuse at the Dursleys' and his journey to find his true self outside of that environment. Another is 'Escaping the Dursleys', which focuses on Harry's early attempts to break free from their cruel treatment.
One interesting 'Harry Potter Dursley fanfiction' could be about Dudley Dursley having a change of heart after the war. He realizes how cruel he and his family were to Harry and tries to make amends. Maybe he starts to study magic in secret, trying to understand the world he once shunned.
One interesting 'Harry Potter Petunia Dursley' fanfic could be one that explores Petunia's childhood and how her relationship with Lily might have affected her view of Harry. For example, a fanfic could show that deep down, Petunia was always a bit envious of Lily's magical abilities, but also loved her sister in a complicated way. This envy could have then translated into her cold treatment of Harry.
The popularity also lies in the fact that it allows fans to expand on the 'Harry Potter' universe. By focusing on the relationship between Harry and Dudley, fanfiction writers can create unique stories that might include elements that were only hinted at in the original series. For example, exploring how Dudley's upbringing in a Muggle family affected his view of Harry's magic, and how that view could be altered in different scenarios.