One interesting plot idea could be Dudley traveling back in time to when his parents first got married. He could see how his family's attitudes towards magic and the Potters were formed. Another could be him traveling forward in time to see the impact of Harry Potter's actions on the wizarding world and how it indirectly affects the Muggle world he lives in. Maybe he travels to a time when a major wizard - Muggle conflict was about to start and he has to use his new - found knowledge of both worlds to prevent it.
A great plot could be centered around Dudley and Harry being forced to work together on a project in the Muggle world that has some unexpected magical implications. This could lead to them understanding each other better and forging a new kind of relationship. For example, they might be involved in an archaeological dig that uncovers a lost magical artifact, and they have to keep it safe from both Muggle and wizarding thieves.
There might be a fanfiction where Dudley gets involved in a magical adventure accidentally. For example, he stumbles upon a magical object that was meant for Harry but now has drawn him into a dangerous yet exciting situation in the wizarding world. He has to learn to rely on his own courage and the help of some unlikely allies.
Another plot could be that the Dursley family gets involved in a magical adventure that has nothing to do with Harry. For example, they accidentally stumble upon a magical artifact that transports them to a different magical realm where they have to learn magic quickly to survive and find their way back home.
Another plot could be a time - travel scenario. A character goes back in time and changes the way the Dursleys treated Harry. As a result, they become a more loving and accepting family. This alteration in their relationship could have a huge impact on the entire wizarding world as Harry grows up with a more positive influence.
In 'Harry Potter and Dudley Dursley' lemon fanfiction, often the character development is a key aspect. Writers might take Dudley, who was a bully in the original series, and transform him into a more sympathetic character. They might show how his experiences with Harry over time, especially in these fan - created scenarios, lead to his growth. And for Harry, it could be about seeing a different side of Dudley that he never expected, which could be quite fascinating to read about.
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.
One idea could be that Ginny and Dudley accidentally meet in a magical mishap. Maybe a spell gone wrong transports Dudley into the wizarding world near Ginny. They initially dislike each other due to their different backgrounds, but as they are forced to work together to get Dudley back home, they start to see each other's good sides.
One common theme is redemption. Many fanfictions focus on Dudley changing his ways after years of being a bully. They show him realizing the error of his actions and trying to make amends.
Maybe they are running in a magical race. Harry uses his broom - flying skills in parts where he can, but Dudley, being more used to running on the ground, finds shortcuts through Muggle - like alleys that are magically connected. Along the way, they meet various magical creatures that either help or hinder them, and they have to figure out how to deal with them as a team.
One idea could be Yoda traveling back in time to train Anakin Skywalker differently, thus preventing his fall to the dark side. Maybe he goes back to the very beginning of the Jedi Order to gain more knowledge about the Force and bring it back to his own time.