Perhaps Voldemort or one of his Death Eaters. Even if it's a more light - hearted fanfic, the presence of a dark force like that could add an element of danger. They might target Potter because of his fame and the twins could get in the middle trying to protect him.
It could be Draco Malfoy. He's always causing trouble for Potter and the Weasley twins would surely not be on his good side either. So he could try to foil their plans and cause problems for them throughout the fanfic.
One possible plot could be that Fred and George, being their mischievous selves, get involved in some sort of magical prank that goes awry. And perhaps Potter, Harry Potter I assume, gets accidentally caught up in it. For example, they could be testing a new product in their joke shop and it causes chaos in Hogwarts, with Potter having to help them fix the mess to avoid getting them all in serious trouble.
Well, perhaps the plot could be about Fred and George getting into some sort of magical mischief together while George is on Fred's back. Maybe they're trying to escape from Filch in Hogwarts and they have to use some unique spells to get away, all while George is piggybacking on Fred.
This fanfic would be different because it focuses on the physical interaction of Fred giving George a piggyback. Most Potter fanfics might be more about battles or romances. Here, it could be a story about brotherly love and support shown in this unique way.
Yes, there are likely fanfics out there with such a scenario. Fanfic writers often come up with creative and unique plotlines. You can start by looking on popular fanfic websites like Archive of Our Own or Fanfiction.net. Just be aware that the quality and nature of these fanfics can vary widely.
Friendship is a very common theme. Since Fred and George are known for their close bond, and when you add Potter into the mix, it often explores how their friendship extends to include him. Another theme could be adventure, with the three of them getting into all sorts of magical escapades.
The main antagonist could be a powerful necromancer who combines the dark arts of Skyrim with some elements of Voldemort - like magic. He could be raising an army of the undead and causing chaos across Skyrim, which Harry has to stop.
It could be a new dark wizard who has a vendetta against Harry. This wizard might use a spell to stop Harry from eating, thinking it will weaken him before a final showdown. He could be someone who was once a follower of Voldemort and now wants to take his place and prove himself by getting rid of Harry.
Maybe an ancient evil spirit that was once bound but is now trying to break free by using the summoner as a conduit. This spirit could be manipulating events from the shadows, causing chaos in the wizarding world to draw the summoner out.
The relationship develops in a way that they understand each other's limitations better. George, being carried, realizes that he can count on Fred in difficult situations. Fred, on the other hand, gets to see George in a more vulnerable state. This newfound understanding makes them communicate more openly. They start to plan their future business ideas with more cooperation, knowing that they can support each other through any challenges that come their way in the wizarding world.
It could be a jealous wizard who was once in love with Hermione. Discovering she has a child with Fred, this wizard might seek to harm the child out of spite. He could use dark magic to try and kidnap the child or cause trouble for the family.