Filming Potter broke existing child labor laws.
The cast of Harry Potter was mostly kids. When they set out to film in England, many of the kids couldn’t work more than four hours a day per the Children and Young Persons Act of 1963. This applied to kids under age 16. Piling on the inexperience of those kids, it made production almost impossible. To keep the film in the UK, British lawmakers made a concession for the film industry only, allowing the kids to work a few more hours, but in some cases, they had to swap out little adults wearing wigs.
Harry Potter’s eyes are green.
In the book, a defining feature of Potter’s eyes, other than his John Lennon (Teddy Roosevelt?) frames, were his green eyes. Everyone knows green eyes are a sign for magical powers. Like Hermione’s buck teeth, filmmakers intended to give the actor a prosthetic, colored contacts. Radcliffe couldn’t do it. They irritated his eyes, so Rowling allowed them to drop it.