Fred and George Weasley are often made even more badass in fanfiction. They could use their prank - making skills in really creative ways during the Triwizard Tournament, like creating distractions for Harry when he needs it.
Neville Longbottom can be an interesting character in such fanfictions. In the fourth year, he might suddenly show a hidden talent for a particular type of magic that helps Harry. For example, Neville could have a natural affinity for herbology - related magic that turns out to be crucial in dealing with some of the challenges in the tournament. He could use his knowledge of magical plants to create barriers or solve puzzles in the maze.
Cedric Diggory can also be portrayed in a more complex and badass way. Instead of just being a competitor, he could be a mentor - like figure to Harry. He could share some of his secrets about handling the tasks in the tournament, and they could form a bond based on mutual respect and the shared danger they face. This would be a different take on their relationship compared to the original story.
A really badass plotline could be Harry having to face a much more dangerous and complex version of the maze in the Triwizard Tournament. Instead of just physical obstacles, there are magical creatures from different realms and dark magic traps. Harry has to use all his skills and knowledge, including some that he's picked up from his interactions with Sirius and Lupin, to make it through the maze alive.
Harry Potter himself is often included. He might be on a new adventure involving magical animals, perhaps trying to protect a rare species from poachers. His bravery and magical skills would be put to the test in these situations.
Fred and George Weasley are very popular in this type of fanfiction. Their mischievous nature can be translated into their rock band personas. They could be the ones coming up with wild stage antics and unique marketing ideas for the band. Luna Lovegood is also a common character. Her dreamy and creative nature might make her a great songwriter or a unique visual element in the band with her eccentric style.
Harry Potter himself would most likely be one of the main characters, as it's about his fourth year and retribution. Hermione and Ron would probably also be important, as they are his closest friends and often involved in his adventures.
Dobby the house - elf can be a popular character in these fanfictions. Writers might have Dobby helping Harry in more creative ways during the Triwizard Tournament. Professor McGonagall is also a favorite, as her strict but fair nature can be explored in different situations during the fourth year. And of course, Sirius Black might make appearances in fanfictions, adding a layer of mystery and family connection to Harry's fourth year.
Luna Lovegood is also quite popular in these fanfics. Her unique personality and way of thinking can add a lot of interesting elements to the story when Harry returns. For example, she might have some out - of - the - box ideas to help Harry in his new adventures.
Obviously, Harry Potter and Severus Snape are the main characters as it's in the title. But often, other characters like Hermione Granger and Ron Weasley are also included. Hermione might play the role of the mediator or the one who helps Harry and Snape understand each other better. Ron could be initially skeptical of their new friendship but later come around.
One interesting plotline could be a deeper exploration of the relationship between Harry and Cedric Diggory before the Triwizard Tournament. Maybe they become unexpected friends and help each other with the tasks in ways not shown in the original book. Another could be a different take on how the other schools' students interact with Hogwarts students. For example, a Durmstrang student might have a secret mission related to the tournament that involves Harry.
Ron Weasley is also popular. He could be a source of comic relief as well as a loyal friend in the new story. If Harry is reborn into a different family or situation, Ron might be one of the first to notice the changes in Harry and help him blend in or deal with any difficulties that come his way.
Obviously, Harry Potter himself is a main character in most of these fanfictions. His journey doesn't end with the defeat of Voldemort, and fans like to explore what he does next.