'Harry Potter': 10 things you never knew about the books and films

— -- It's been 20 years since "Harry Potter and the Philosopher's Stone" arrived in U.K. bookstores.

Four years later, Daniel Radcliffe, Emma Watson and the gang would take up the mantle on the big screen. Over the last two decades, the books and films have captivated both young and old.

Here are 10 fun facts you probably never knew about the "boy who lived."

1 - Why Harry's eyes weren't green in the films like in the books.

In the DVD extras for "Harry Potter and the Deathly Hallows – Part 1" in 2011, author J.K. Rowling and Radcliffe discuss why they changed that important part.

Radcliffe, who has blue eyes, had tried on green contact lenses, but he found them uncomfortable, so Rowling said the only important "thing is that his eyes look like his mother’s eyes. So if you’re casting Lily, there needs to be a resemblance."

"There is a very small percentage of people apparently who have a very extreme reaction to contact lenses. And I was one of them," Radcliffe added.

2 - Robin Williams rejected?

Yep, the late Oscar winner wanted to play Hagrid in the movies, but apparently there was a Brits-only rule by the producers.

“Robin had called [director Chris Columbus] because he really wanted to be in the movie, but it was a British-only edict, and once he said no to Robin, he wasn’t going to say yes to anybody else, that’s for sure,” casting director Janet Hirshenson told the Huffington Post last year.

3 - What's up with Hermione Granger's teeth?

Another change from the book was Hermione's buck teeth. Christopher Columbus, the director of the first two films, said fake teeth were only used for one scene in the very first film.

"I realized that she's never going to be able to perform with these huge fake teeth in her mouth for the rest of the movie," he told EW. So he took them out for the rest of the movie and the rest of the franchise.

4 - Voldemort's nephew?

Well, kind of. One of the actors who played young Tom Riddle, the orphaned boy who eventually became the dreaded Voldemeort, is actually Hero Fiennes-Tiffin, the nephew of Ralph Fiennes, who played the dark wizard.

5 - J.K. Rowling the actress?

Rowling said she was offered the role of Lily Potter, Harry's mother, in the very first movie, but turned it down.

"I really am not cut out to be an actress, even one who just has to stand there and wave. I would have messed it up somehow," she said, according to the U.K. Telegraph.

6 - American and UK versions.

Fans who flocked to the theater more than 15 years ago to see "Harry Potter and the Sorcerer’s Stone" noticed that the title of the first movie had changed from the book, which was called "The Philosopher’s Stone."

Hagrid's dialogue in the book was also changed for U.S. moviegoers.

7 - Rowling regrets Hermione and Ron getting together.

In an interview with the Sunday Times, the scribe admits that she later wanted Harry to be with Hermione but stuck to the original story she created all those years ago.

"I wrote the Hermione/Ron relationship as a form of wish fulfillment. That’s how it was conceived, really, for reasons that have very little to do with literature and far more to do with me clinging to the plot as I first imagined it," she told the paper.

Hermione and Harry might have been a better match, she added.

8 - Where Harry Potter came from

Rowling picked the name Harry Potter because Harry "has always been my favorite boy's name, so if my daughter had been a son, he would have been Harry Rowling," she told Scholastic.com in 2000.

As for Potter, it "was the surname of a family who used to live near me when I was 7 years old and I always liked the name, so I borrowed it," she said.

9 - The King of Hogwarts?

In 2010, Rowling told Oprah Winfrey that Michael Jackson wanted "Potter" to be a musical.

"I said 'no' to a lot of things," she said.

10 - Radcliffe almost wasn't Harry.

Famed director Steven Spielberg, who was originally slated to lead the first film, wanted Haley Joel Osment from "The Sixth Sense" to play the title role.

But Spielberg dropped out and later told the BBC that while he knew the film would be a hit, it just didn't touch his heart the way it did for fans.

The rest is history and Radcliffe ended up being cast.

For his part, Joel Osment actually later said that he loved the books, but wasn't too excited about the movies coming out. Looks like the right actor became Harry.

ABC News' Morgan Korn contributed to this report.