Well, in this fanfiction, a plot twist could be that Harry has some sort of magic that is only activated by his new family connection to Arthur. This magic could be something that is both a blessing and a curse. It could attract unwanted attention from dark forces. Another plot twist could be that the Weasley family has a hidden past related to Harry's parents that comes to light because of this new family relationship. This could change how Harry views his parents' death and his own role in the wizarding world. And maybe there is a character within the Weasley family who is not what they seem, and Harry's new position as Arthur's brother makes him the only one who can uncover the truth.
One plot twist could be that Voldemort tries to use Harry's new family ties to get to Arthur and the Ministry. Another could be that Harry discovers some long - hidden family secret that changes his view of the Weasley family and his place in it.
One plot twist could be that Harry's real father was not James Potter but an unknown figure from Hawkgirl's world. This would completely change the dynamics of his family story. Another could be that Voldemort discovers Harry's Hawkgirl heritage and tries to use it against him by creating a spell that combines dark magic with the technology or powers associated with Hawkgirl's world.
One possible plot twist could be that Harry, as James' brother, has a different role in the fight against Voldemort. Maybe he's more of a behind - the - scenes strategist. Since he's in the family earlier, he could have different relationships with the other characters too. For example, his bond with Sirius might be even stronger as they grow up together more closely.
Well, it could be that Harry, as James' brother, discovers that there were more secrets about his first life than he thought. Maybe he finds out that there was a hidden power within him that was never fully awakened in his previous life. This new discovery could change the way he approaches magic and his role in the fight against the Dark Arts, and it might also lead to a different ending to the battle against Voldemort.
A plot twist might be that Harry's past enemies from the wizarding world somehow find a way to cross over into the Naruto world. This would force Shikaku and Harry to team up not only with the ninjas but also with some of Harry's old friends from Hogwarts. It would create a really chaotic and interesting situation where two different worlds' powers and skills collide.
A really interesting plot twist in some fanfictions is that the Hogwarts houses are not what they seem. For example, Gryffindor was originally founded to be a sort of 'cover - up' for a secret society within Hogwarts that had a much darker purpose. Or that Slytherin was actually trying to protect the wizarding world from an even greater evil, but his methods were misinterpreted. This changes the whole dynamic of the story and how we view the different houses.
A potential plot twist could be that Harry actually has a hidden agenda. He accepts Voldemort's offer just to get closer and find a way to defeat him from the inside. He might pretend to be on Voldemort's side while secretly working against him.
One interesting plot twist could be that Harry discovers he has the ability to communicate with the Basilisk on a deeper level than just Parseltongue. Maybe he can see through the Basilisk's eyes and use this to his advantage in uncovering secrets within Hogwarts that even Dumbledore doesn't know. Another could be that the Basilisk is not truly a villain but was being controlled by a dark force all along, and Harry has to find a way to break that control and free the Basilisk.
One interesting plot twist could be that the basilisk has an unexpected alliance. Maybe it teams up with a group of outcast magical creatures to take revenge on those who have wronged them. This would completely change the dynamic as in the original, the basilisk is mainly a tool of Voldemort.
In this fanfiction, a great plot twist might be that the gamer's knowledge of game strategies is used to outwit Voldemort in a completely unexpected way. Instead of a traditional magical duel, the gamer uses their understanding of leveling up and collecting power - ups to somehow weaken Voldemort's magic. Maybe they find a way to 'hack' into his dark magic, using skills from the game world that no one in the wizarding world had thought of before.
Well, in some 'Harry Potter and the Prophecy' fanfiction, a plot twist could be that the prophecy was not a prophecy at all but a spell cast by an ancient wizard to set in motion a series of events for a greater purpose. For example, it was to bring about a new era of magic where Muggle - borns and pure - bloods could co - exist peacefully. This would completely change the way the characters view the prophecy and their roles in it. Also, the prophecy might be tied to a different character than Harry or Voldemort, like a minor character who suddenly becomes central to the whole story.