Has that happened [disagreements] on any of the films?
There’s one moment in "The Chamber of Secrets" that I don’t like, where Hagrid enters Hogwarts at the end of the movie and the whole group of assembled students applaud him. That would not happen. And it really upset me. I felt it was a real violation of character. And that was odd because [director] Christopher Columbus is a Potter fiend. He carried the book around with him. You could never catch Chris on anything. But I think Chris felt that he wanted the release of that moment. It was a mild disagreement.

What, if anything, can you say about the climactic moment between Snape and Dumbledore? In the book, it’s a short but intense scene.

It is informed by everything [Potter readers] have come to know is true. So if you watch the film carefully, there are performance moments that are quite extraordinary, Alan Rickman [who plays Snape] especially. There is something we added that you can look forward to, a short scene between Harry and Snape prior to the big event. It’ll be interesting to see how it plays to the audience. It should be a haunting moment for Harry. While I was writing, I just had a notion about a moment between him and Snape, something Harry could look back on and question as to why he didn’t act differently.

I’ve also read that most of Dumbledore's pensieve memories of young Voldemort, then Tom Riddle, have been cut from the film. (Not to mention: Dumbledore's funeral!)

In my original draft, I had every single memory but one, I believe. I even dramatized a couple of things that weren’t in the book in terms of Voldemort, like the death of Tom’s parents, things like that. I'm a Harry Potter fan, so my first drafts tend to reflect that, in that they tend to be long and all-inclusive. When [director] David Yates came in, he had a very specific point of view, which was that he wanted to showcase Voldemort’s rise without getting overly involved with his past as Riddle. He didn’t think that most of the memories would be as compelling on-screen as they are on the page. He liked them in the script, but he really felt that in the movie experience Voldemort’s story was more important than young Riddle‘s. We went back and forth on that for quite a bit. But he was very convincing, and I think it wound up working out well.

Why didn't you decide to adapt "Order of the Phoenix"?

You know, I don’t even know why. The fourth film, "Goblet of Fire," was really hard to do. I wrote on it for two years. But it’s not that simple and I don’t know that I’ll ever fully understand why I didn’t do it. This will sound glib, but it’s somewhat true: They asked me on the wrong day. They asked me for the last time on the wrong day. Had they asked me the next day, I probably would have said yes. There’s always stuff that goes on around these movies and I felt an urge -- and I still feel an urge -- to do other things. To go back to making movies nobody wants to see, and I'll do so. But I think I was feeling that urge particularly keenly at that time. I always said too that if the kids left, I would leave too. And there was some talk about Emma Watson [who plays Hermione] leaving and that would have been hard for me if Emma had left because I like writing for the three kids.