Hermione is a very common character. Given her intelligence and magical skills, she often plays a crucial role in saving Harry. Ron is also often involved as Harry's loyal friend. Dumbledore, even in fanfiction, is a character who might show up to save Harry or at least guide the others in the rescue.
In a lot of 'harry gets saved fanfiction', Sirius Black is a character that could potentially save Harry. He has a strong bond with Harry and his abilities as an Animagus and a powerful wizard make him a likely candidate. Ginny Weasley, too, with her feisty nature and growing magical abilities, can be a key figure in saving Harry in these stories.
The Weasleys are very common. Given their big hearted nature and their closeness to Harry in the original story, it makes sense for them to adopt him in fanfiction. They already treat him like family, so it's a natural fit.
Obviously, Harry Potter himself is the central character. His friends like Ron Weasley and Hermione Granger are also often involved. They might try to visit him while he's grounded or come up with plans to get him out of being grounded. Dumbledore could also play a role, either as the one who enforces the grounding in some cases or as the one who might offer some wisdom to Harry during his time of confinement.
Dumbledore could make an appearance in the form of a guiding spirit or through memories. His wisdom could be crucial for Harry as he navigates the new situations outside of town.
Sometimes, new original characters are created in fanfiction to help Harry. These could be students from other wizarding schools who have unique skills. For example, a student from a school in a far - off land who has mastered a type of magic that is unknown in Hogwarts and uses it to help Harry in his fight against the dark forces.
Hermione would be a common character. She would likely be very determined to find Harry and bring him back. She might use her vast knowledge of magic and research skills to track him down.
Well, in certain 'harry gets saved fanfiction', Hermione might use her vast knowledge of magic in a completely new and unexpected way to save Harry. She could combine different spells and charms that no one has thought of before. Also, there could be fanfictions where Neville, having grown in confidence and power, is the one who saves Harry from a life - threatening encounter with a dark wizard.
Obviously, Harry Potter himself is the central character as he's the one getting the wish. Hermione and Ron are also commonly involved. They are Harry's best friends, so they would be there to support him or perhaps even influence his wish. Dumbledore also often shows up in these fanfictions. As the wise headmaster, he might guide Harry on how to use his wish wisely or warn him of the consequences.
Hermione is often a key character. She might stand by Harry's side, using her intelligence and loyalty to help him through the tough times. She could be the one to encourage him to keep going and not let the disownment break him.
Hermione Granger is a very common character. Since she is Harry's best friend, she would likely be there to help him understand and control his new superpowers. She might research in the library to find out how these powers came about and how to use them effectively. Ron Weasley is also common. He would probably be both in awe and a bit jealous of Harry's new powers at first but would still support him in the end.
One common theme is probably the idea of rescue and heroism. BTS members are often depicted as the heroes who save the reader from drowning, showing their brave and selfless side.