Maybe some of the Hogwarts professors like Professor Sprout. After all, she's the Herbology teacher. She could give Harry some expert advice on how to grow different kinds of food plants. She might even let him use some special greenhouses or tools in the school for his food - growing projects.
Another possibility is that he uses some ancient magic that he discovers in the Forbidden Forest or some old wizarding books. This magic could be more in tune with nature and be used specifically for growing food. It might involve some sort of connection with the earth and the natural cycles of growth.
He could use the Herbivicus Charm. This charm is often used to make plants grow. In the fanfiction, it might be enhanced to quickly grow all kinds of food crops like pumpkins, carrots, and strawberries. It would be really cool to see Harry using this charm in a big field and within seconds, there are rows of fresh, ripe vegetables.
Definitely Ginny. Since she's Harry's love interest in the original series, in the fanfiction about them growing up, she has a big role. She could be shown as a strong, independent witch who is equal to Harry in many ways. Draco Malfoy is also a character that features a lot. Sometimes, fanfiction explores his redemption arc further as he and Harry have to interact in the post - war wizarding world.
There could be many amateur authors out there who might write such a fanfiction. It could be a young, creative Harry Potter fan who loves to imagine new and exciting adventures for the characters. They might be inspired by their love for the series and the idea of giving Harry a new and unique ability like growing wings.
Hermione could be another main character. Maybe she discovers what's happening to Harry and the author and tries to find a way to reverse it or at least understand it better. She could use her vast knowledge of magic to research the phenomenon.
It could be Sirius Black. Since he has his own experience with Azkaban, he might know some secrets about the place. He could return in some form within the fanfiction and assist Harry in his escape, maybe by leading him through some hidden tunnels or using some special skills he developed during his time in prison.
Yes, there are some fanfictions out there where the two universes cross paths and Harry Potter might help Superman in some way. You can try searching on popular fanfiction websites like FanFiction.net or Archive of Our Own.
Yes, there are some out there. Some fanfictions might explore the idea of Harry Potter helping Voldemort in an alternate universe where their goals are misaligned or there are complex magical reasons for it. For example, in a situation where Harry believes he can change Voldemort's ways by getting closer to him, rather than fighting him directly.
One great fanfiction where Snape helps Harry Potter is 'The Unseen Bond'. In this story, Snape secretly protects Harry from a new dark threat at Hogwarts. He uses his knowledge of the Dark Arts to counter the enemy's spells. This shows a different side of Snape, one that is more benevolent towards Harry.
Hermione could be the one. With her vast knowledge of the wizarding laws and her sharp intellect, she might dig up some old regulations that prove Harry's right to his money. She would then fight tooth and nail in the wizarding courts or against the goblins at Gringotts to get his money back.