Well, perhaps Harry could face unexpected magical challenges. The Goblet might summon him for a task that is far more dangerous than the Triwizard Tournament in the original story.
Maybe it's a character who was previously thought to be good but has been corrupted. They use the Goblet's summoning of Harry to create chaos in the wizarding world. For example, a teacher at Hogwarts who has secretly turned to the dark side. They could manipulate the events surrounding Harry's summoning to turn the students and faculty against each other, all while trying to achieve their own sinister goals.
One interesting plot in this kind of fanfiction could be that the Goblet of Fire is actually under some dark magic influence. Harry, being summoned, discovers this conspiracy. He then has to not only deal with the Triwizard Tournament tasks but also find a way to break the dark magic's hold on the Goblet. This could involve him delving deeper into ancient magic lore and seeking help from the Forbidden Forest's creatures that are often overlooked in the original story.
Well, perhaps in this fanfic, the Goblet of Fire might summon Harry in a different way than in the original story. Maybe it has a mind of its own and specifically targets Harry for a more dangerous and secretive task that the original Triwizard Tournament didn't include.
It could be a powerful dark wizard who has infiltrated the Ministry of Magic and manipulated the Goblet of Fire. They might want Harry out of the way to further their own dark plans.
There is also a possibility that the main antagonist is the Goblet itself if it has been corrupted by some ancient dark magic. It could be summoning Harry not for a normal Tournament but to sacrifice him or use his power for some evil purpose, making the Goblet the force that Harry has to fight against.
Well, he might face some unexpected challenges. In fanfiction, the author could take the plot in all kinds of directions. Maybe he'll be forced into a dangerous tournament that's even more perilous than in the original story. He could encounter new magical creatures or spells that are unique to this fan - created scenario.
The plot could develop in a way that Harry is transported to a different realm or time period. In fanfiction, the Goblet's summoning power could be more than just for a tournament. He could end up in a place where the magic is different, and he has to adapt quickly. He might meet versions of his friends or enemies that are very different from what he knows, and this would greatly influence the story's development.
One common theme is identity. Since Harry is now female, she has to re - evaluate who she is in the wizarding world. Another theme is relationships. Her friendships and potential romances change. For example, her relationship with Ron might be different as there could be a bit of jealousy from Ron in a different way than in the original story. Also, the theme of facing challenges as a female in a male - dominated magical society is often explored.
He might be more confident. Since he's from the future, he has already faced many challenges and grown from them. So, in the fanfiction, he could be more self - assured when dealing with the likes of Snape or Malfoy. For example, he might not be as easily intimidated by Snape's sarcasm.