Dan Radcliffe, Emma Watson, and Rupert Grint sign on for each movie one at a time. This allows them to opt out if they feel they no longer want to take part. So far, the cast has made no real visible signs of not wanting to continue in their roles. Usually before casting is announced for each movie there are a series of wild rumors indicating one (or more) of the trio will be recast/replaced/leaving.

Currently, Order of the Phoenix is under way.

Without making the movies three and four hours long, many things that are not central to Harry and his journey through Hogwarts are likely to be cut. Things that are important are likely to be abbreviated, and characters are likely to get lines/duties that are performed by other characters in the books. The movies are very likely to stay at or below the two and a half hour mark.

She writes: "I was fine with it. It is simply impossible to incorporate every one of my storylines into a film that has to be kept under four hours long. Obviously films have restrictions novels do not have, constraints of time and budget; I can create dazzling effects relying on nothing but the interaction of my own and my readers' imaginations - hence my preference for the page over the screen."

From JKRowling.com:
Spells in the films - there I've lost track. Steve invented some and I gave him others. Some of the new incantations, such as 'lacarnum inflamari' must have sounded more dramatic onscreen - although by the time you've managed to say 'lacarnum inflamari', you've surely lost precious seconds in which the Devil's Snare might have throttled you. But that's showbiz.

JK Rowling has resisted suggestions by filmmakers that the movies should be filmed in the United States or cast with American actors (only one American appears in the first film). As they are her books, she does get a large say in this regard.

She writes, "I must admit, I was taken aback when I saw the film Flitwick, who looks very much like a goblin/elf (I've never actually asked the filmmakers precisely what he is), because the Flitwick in my imagination simply looks like a very small old man."

Furthermore, "Flitwick has a background that I now realise will never see its way into the books because it is not relevant to the plot. He is human but with a dash of goblin ancestry - something like a great, great, great grandfather. This is only interesting in as much as it gives him a perhaps unexpected empathy for people like Hagrid who are, in Death Eater parlance, half-breeds. However, Flitwick and Hagrid have never had a scene together, so Flitwick's genetic composition has been relegated to the very back of my mind over the six novels in which he features, although I think it has informed his character. Slightly dotty though he may be, he is welcoming of all students, whatever their background (he did say in 'Philosopher's Stone' that he was very fond of Lily, thus establishing that he was not prejudiced against Muggle-borns)."

They are located with the corresponding book under "The Books" section on the menu.