One interesting plot twist could be Draco secretly helping Harry Potter in the Triwizard Tournament tasks. Maybe he realizes that there's a greater danger at play that could affect both the wizarding world and his own family, so he decides to put aside their rivalry for a while.
In some fanfictions, there might be a plot twist where Draco is actually a part of a secret organization within Hogwarts that has something to do with the Goblet of Fire. This organization could be working against the Death Eaters or some other dark force in the wizarding world. It would completely change the way we see Draco's character as he's usually portrayed as a bit of a bully on Voldemort's side.
A really unexpected plot twist could be that Draco is the one who was supposed to be in the Triwizard Tournament all along, but due to some magical interference or a prophecy, Harry was chosen instead. This could lead to a whole new set of adventures and interactions between Draco and Harry as Draco tries to prove that he should be the champion and Harry tries to figure out why he was chosen in the first place.
A possible plot twist is that Draco is secretly helping Harry in the Goblet of Fire tasks. He might do this because he realizes that there are darker forces at play that could harm not just Harry, but also Hogwarts and his own family. So, he uses his knowledge of the dark arts in a positive way to assist Harry without anyone knowing.
One interesting plot twist could be that Harry has an unexpected ally in the Triwizard Tournament. Maybe a Slytherin student who has a hidden agenda but ends up helping Harry in a crucial task. This would change the dynamic of the traditional House rivalries.
In some fanfictions, Draco might start to question his family's loyalty to Voldemort. The events of the Goblet of Fire could expose him to the true horrors of the Dark Lord's plans, causing him to develop a more independent and moral stance. For example, he could see the harm that Voldemort's return brings to Hogwarts and its students, and this makes him reevaluate his associations.
One interesting plot twist could be that instead of Cedric Diggory being the Hogwarts champion, Neville Longbottom is chosen by the Goblet of Fire. This would completely change Neville's character arc in this part of the story, as he'd have to face much more danger and scrutiny. It could also lead to new friendships and rivalries.
One interesting plot twist could be that Hermione is secretly entered into the Triwizard Tournament not by the Goblet, but by a dark wizard who wants to use her as a pawn. This would put her in a very dangerous situation right from the start.
One interesting plot twist could be a character who was thought to be a friend actually being in league with the Death Eaters all along. For example, a minor character like Seamus Finnigan could be secretly working for Voldemort, passing information about Harry's movements. This would add a whole new layer of danger and suspicion to the story.
One interesting plot twist could be that Fem Harry forms an unexpected alliance with a Slytherin student. Maybe she realizes that not all Slytherins are as bad as they seem in the context of the Triwizard Tournament. This changes the whole dynamic of the story as she now has an inside source in a house that was previously seen as her rival.
A great plot twist could be that the Goblet of Fire was actually tampered with by a group of former Death Eaters who wanted to bring back Voldemort in a different way. They planned to use the tournament as a cover to perform a dark ritual, and Harry uncovers this plot halfway through the story.
In some of these fanfictions, a great plot twist is that Draco, being a Muggleborn, is actually a long - lost heir to a powerful Muggle - related magical artifact or prophecy. This throws the whole wizarding world into chaos as different factions try to either use him or protect him. Also, there could be a plot twist where Draco uses his knowledge of the Muggle world to outwit dark wizards. Since he has a connection to the Muggle world that most pure - bloods don't, he can come up with strategies that are completely unexpected, like using Muggle technology in a magical way to defeat his enemies.
One interesting plot twist could be that a different student is chosen by the Goblet of Fire instead of Harry. Maybe a Slytherin student who then has to deal with the suspicion of being in cahoots with Voldemort. Another could be that the tasks in the Triwizard Tournament are completely different, like instead of facing a dragon, they have to solve a complex magical riddle within a dangerous enchanted forest.