Obviously Harry would be one of the main characters. And Hermione might also be involved, perhaps she helps Harry get the job or gives him advice on how to do it well.
Ron could be in it too. He and Harry could work together at the same place. Maybe they get into some funny situations because of Ron's carefree attitude.
Obviously, Harry would be the main character. His friends like Hermione and Ron could also be important. Hermione might help Harry with the intellectual aspects of his job, like research or paperwork.
Well, he could work at Hogwarts during the summer for a change. Maybe he's helping Hagrid with the care of magical creatures. He would get to interact with new and dangerous beasts, and at the same time, he might learn some new spells to keep them in check from other professors.
Well, he might work at Weasleys' Wizard Wheezes. He could help George and Ron with inventing new products and dealing with customers. It would be full of magical mishaps and lots of fun.
He could work at Weasleys' Wizard Wheezes. He has a good relationship with the Weasley family, and it would be a fun place for him to work, helping with inventing and selling all kinds of magical pranks and toys.
He could meet other young wizards and witches who are also working summer jobs. Maybe some from other wizarding schools.
Hagrid could be a great help. He has a lot of connections in the wizarding world, especially with those related to magical creatures. He might introduce Harry to someone who needs help with taking care of or studying magical beasts, and thus get Harry a job in that area.
Hermione could be one of the main characters. She might be the one who first notices Harry's change and helps him navigate through the new attention he's getting. She could also offer her wisdom on how to handle the situation without letting it go to his head.
In this fanfic, Harry might get a job as an Auror. He would be involved in solving magical crimes, going on dangerous missions, and working with his old friends to keep the wizarding world safe.
The main characters in the 'Harry Potter 4th Summer Fanfic' could be Harry Potter, of course, as the central figure. But Fleur Delacour could be introduced early in the summer, maybe she has some business at Hogwarts or in the wizarding world near where Harry is. Viktor Krum might also make an appearance, perhaps he is scouting the area where the Triwizard Tournament will be held. And Ginny Weasley could be a main character as well, she might be developing her own magical abilities and sharing some of her insights with Harry.
In this fanfic, Harry Potter is the protagonist. He is the one with the idea of giving the troll a job. The troll is the main character as well, as the story focuses on its new life with a job. Additionally, Dumbledore might be involved. He could be either supporting Harry's decision or warning him about the potential risks of having a troll in a certain role at Hogwarts.