Q. What amazes you about Harry Potter fans?

A. The amount of knowledge they have about that universe.... There was a kid who came on the set of the first film, and he couldn't have been older than 7. It was during the Christmas scene at Hogwarts. He watched as people were pulling open crackers in the Great Hall, and ... said, "That's wrong." And Chris (Columbus, the director) said, "What do you mean?" And the kid said, "There should be mice coming out of the crackers." Apparently, that was in the book.

Kloves will soon start "The Half-Blood Prince." "They want to film the two as close to back-to-back as they can," Kloves says. "Because the kids are really starting to grow up. And if we lose the kids, if they have to recast for six or seven, I think we will lose the movies. That's what makes them magic."

"This is a coming-of-age story for Harry," he says. "And at some point he has to make the journey alone. Which he can't if Dumbledore is around to protect him." But he has no idea whether Professor Severus Snape is guilty of murdering the beloved Hogwarts headmaster. He is happy that Snape plays such a large role in the sixth book, mainly because he loves writing for Alan Rickman, who plays the professor.

"It's hard because if you look at the books, Snape really just sort of hovers, as a threat, more than actually does something," Kloves says. "And Alan is just a wonderful actor. He always says the lines exactly as I write them, including the ellipses. I have never met an actor who could act out ellipses, but Alan can."

Likewise, he was hoping, for example, that the character of Draco Malfoy would come more into the fore in "Goblet." "Tom Felton [who plays Malfoy] is such a wonderful actor," Kloves says. "I was hoping that Draco would become a little more dangerous." That seems to have happened in "Half-Blood Prince," but again, Kloves has no way of knowing exactly where the character is going. He was pleased to be able to give Rupert Grint, who plays Harry's best friend, Ron Weasley, room to stretch in "Goblet of Fire." Grint, he says, is such a natural-born comedian that the filmmakers have to fight the urge to let him become simply the comic relief. "In 'Goblet' we gave him some brass, which made me very happy. Rupert is amazingly funny, but I didn't want him to become Abbott to Harry's Costello."

“It never felt odd to me because all of my [prior work] had to do with dysfunctional families, kids who have been damaged, and damaged people. To me, Harry is the ultimate damaged character… right down to his scar.”

She's your favorite character, right?

Yeah, I always loved Hermione because I thought she was the kind of girl that would have driven me crazy in school and that I would have been desperately in love with. So smart and funny.

Q: So what are your plans once Fred and George are kind of not in the Hogwarts scene anymore, like for the next movie?

J: Um, I’d stay in something in the industry. I’ve been doing a bit: About two months, I’ve been what’s called “running,” which is sort of like ... go between different departments behind the camera on the new “Da Vinci Code” film. Um, a few of the guys who do the back crew on “Potter” went on to do “Da Vinci.” and I said, “Well, if you ever need someone to help out, give me a ring.” And so they did. And so I’ve been doing that for a few weeks now, and that’s finished, and they’ve gone on to another film, which they’ve asked me to go and help with, so hopefully something like that.