In a fanfic, Harry might be having trouble sleeping because he senses a new dark force approaching Hogwarts. He lies awake at night, listening for any strange noises. Ron tries to cheer him up by telling him funny stories from their previous adventures, but it doesn't really help. Eventually, they decide to explore the Forbidden Forest at night to find out what's causing his unease.
One main theme could be the complex relationships within families. In the Harry Potter universe, family is often a mix of blood relations and found families. In this fanfiction, it might explore how characters deal with family members who have different values or loyalties. For example, Harry's relationship with the Dursleys is always a point of conflict, and the fanfiction could expand on that by showing how he overcomes or continues to struggle with their mistreatment.
They might face a powerful dark wizard. In fanfiction, there are often new villains created. This new dark wizard could be after something they have, like an ancient magical artifact that Harry and Ginny are protecting.
Harry Potter is bound to be one of the main characters. Since it's about 'double trouble', there could be a version of Harry that is different in some way, like an evil Harry or a Harry from an alternate dimension. Ron and Hermione would be there to support the real Harry. Dumbledore might also play a significant role as he often has the wisdom to deal with complex situations. And, of course, Voldemort could be a central figure as well, as he is the main antagonist in the Harry Potter series and any double trouble might be related to the battle against him.
They might use their combined magical skills. Harry is known for his powerful Patronus charm, and Ginny is a very talented witch. They could use these skills to fight off whatever is causing the trouble.
Luna Lovegood might be a great character in this fanfiction. Her own family situation is a bit different and she has a very open - minded view of the world. She could be a source of comfort or inspiration for characters dealing with family trouble, and her quirkiness could add a new dimension to the story.
The 'trouble with imps' in a Harry Potter fanfic might also be about how difficult it is to control or get rid of them. Imps are not as powerful as some other magical creatures but they are very tenacious. If they've infested a certain area of Hogwarts, like the Forbidden Forest or an old, unused classroom, it would be a headache for the teachers or the caretaker, Filch. They might try different spells to banish the imps, but the imps keep coming back, causing continuous trouble.
It can use magic elements. For example, a character could be under a spell that disrupts their sleep. The solution might be to find a counter - spell or a magical herb.
One possible plot idea could be two versions of Harry Potter existing simultaneously in Hogwarts, causing chaos as they both try to deal with Voldemort in different ways. Another could be that a spell creates double trouble for Harry, like his magic splitting into two opposing forces that he has to reconcile.
One fanfiction I remember has to do with a student finding a hidden room in Hogwarts that was used by the founders for some dark experiments. As they start to uncover the secrets of this room, they attract the attention of not - so - friendly spirits and magical beings, which causes a great deal of trouble. It's a really exciting read as it delves deep into the possible hidden history of Hogwarts.