Found on MentalFloss
1. Hermione’s name was almost “Hermione Puckle.” It has a sour tone to it, doesn’t it? J.K. Rowling thought so, too, and changed to something that suited the character better. Rowling has said that Hermione has a healthy dose of herself in there, as she was quite the know-it-all herself as a child. Hermione was originally going to have a younger sister, but Rowling never found the right moment to stick her into the books.
2. Gilderoy Lockhart, the insufferably vain professor and celebrity from The Chamber of Secrets, was based on someone Rowling knows in real life. The rumor is that she based him on her ex-husband, but she has been quite adamant about denying that. “He used to tell whopping great fibs about his past life, all of them designed to demonstrate what a wonderful, brave and brilliant person he was. Perhaps he didn’t really believe he was all that great and wanted to compensate, but I’m afraid I never dug that deep,” she has said. “He’s probably out there now telling everybody that he inspired the character of Albus Dumbledore. Or that he wrote the books and lets me take the credit out of kindness.”
3. Hedwig, Harry’s Snowy Owl, isn’t entirely accurate. After the first book was accepted for publication, she found out Snowy Owls are diurnal. And it was during the writing of book two that she realized that Snowy Owls are silent, meaning that Hedwig’s knowing hoots and conversational noises weren’t quite true-to-life. She admits this was just a research hole on her part, but says readers should feel free to assume that her unusual talents are just part of her magical ability. Incidentally, although Hedwig is female, she is played by a male in the movies because females aren’t wholly white like males are.
4. Collecting unusual and interesting names and words has been a lifelong habit for Rowling. She has said that she loves reading lists of them, from war memorials to baby name books, and made it a point to remember her favorites. Some of them found a new home in the Harry Potter books. She makes up some of the words too – “quidditch” is a Rowling original. She filled up five pages of made-up words that started with “Q” before she hit on one that sounded right. “Voldemort” and “Malfoy” were also invented.
5. If a muggle were to happen across Hogwarts, all they would see is nothing but a ruined castle with large signs on it saying ‘keep out, dangerous building.’ This might sound a bit suspicious to those of us in the States, but it seems like the U.K. is rife with castle ruins.
6. Fred and George Weasley were born on April Fool’s Day. Go figure. While we’re talking about the Weasleys, there was a Weasley cousin named Mafalda who got edited out of The Goblet of Fire in order to make room for the love-to-hate-her invasive “journalist” Rita Skeeter. That’s probably best – Ginny Weasley is supposed to have been the first girl born to the Weasley family for several generations, so scrapping Malfalda supports that backstory.
7. Harry, Ron and Hermione all have wand cores based on their birthdays: the Celt assigned trees to people based on that kind of like we assign gemstones today. She had already assigned Harry’s holly-based wand when she discovered the Celt tree calendar and found that she had accidentally assigned him the “right” type of wood. She did the same thing with Draco Malfoy (Hawthorn wood). But Ron and Hermione both purposefully received wands based on their birthdays – ash for Ron and vine wood for Hermione. She didn’t carry this convention out for all of the characters, though.
8. Filch’s cat, Mrs. Norris, takes her name from the Jane Austen book Mansfield Park. Fittingly, Austen’s Mrs. Norris is also rather sour and bitter.
9. Snape was partially based on a teacher J.K. Rowling once had. She likes to write him, though, because she finds him such a pathetic creature.
10. As you probably know, King’s Cross station is where young wizards hop on the Hogwarts Express to get to school. What you might not know is that the station holds special meaning for J.K. Rowling: it’s where her parents met. They were coincidentally both headed to Arbroath in Scotland when they met on the train. King’s Cross was intentionally chosen as the gateway to Hogwarts in homage to Rowling’s parents.