Mrs. Dilber is not one of Charles Dickens' most famous characters.

Still, Ebenezer Scrooge's spunky housekeeper became a favorite of director Paul McCusker and his Radio Theatre (www.RadioTheatre.org) team during its production of "A Christmas Carol." As a tribute, characters named Dilber were written into the Father Gilbert Mysteries and "The Legend of Squanto," while a "Dilberius" appeared in a biblical series.

McCusker also decided to continue this inside joke in his first radio script for "The Lion, the Witch and the Wardrobe," turning a housekeeper named "Mrs. Macready" into yet another "Mrs. Dilber." Douglas Gresham, the stepson of author C.S. Lewis, jumped on this tiny change as soon as he saw the script.

"His logic was simple," recalled McCusker, laughing. "He said that the diehard fans will know that it's supposed to be Mrs. Macready because millions of them know these books cover to cover. Diehard fans will know we changed it and, for them, that will affect everything. Then they'll start calling and writing, wanting us to change the name back to Mrs. Macready. Why go through that?"

It was nearly a decade ago that McCusker began dramatizing "The Chronicles of Narnia," the Oxford don's fantasy series that has sold nearly 100 million copies in the past 55 years. Thus, McCusker has already worked his way through some of the creative and even theological issues faced by movie director Andrew "Shrek" Adamson and the rest of the team that has turned "The Lion, the Witch and the Wardrobe" into a $150 million epic for Walden Media and Walt Disney Studios. Adamson has also worked closely with Gresham, whose mother, American poet Joy Gresham, married Lewis late in life.

Legions of Lewis fans must realize, said McCusker, that turning books into movies requires changes. Today's digital artists can show in mere seconds what, in print, required many paragraphs to explain. Meanwhile, dramatic scenes that Lewis quickly sketched -- such as massive battles involving talking beasts and magical creatures -- will be expanded because this is what modern audiences want to see fleshed out on screen.

"You have to make choices, but you have to make careful choices. If you take a major scene out, or you make a big change in the plot of a book that is this beloved, you are going to hear about it. Just ask Peter Jackson," said McCusker, referring to the director of "The Lord of the Rings" movies.

Gresham, 60, is serving as co-producer of the Narnia project. He stressed that he has, "for 30-odd years," dedicated himself to finding artists and entrepreneurs who share his commitment to faithfully capturing the themes in his stepfather's books.

"It is my ambition to live long enough to see all seven Narnian Chronicles made into feature films," he said, during a recent visit to Washington, D.C.

Because of recent leaps in technology, insiders realized that "now is the time to make this movie," said Gresham. "If you can imagine it today, then we can film it. ... But I don't want people coming out of 'The Lion, the Witch and the Wardrobe' saying, 'Wow, what tremendous special effects.' I want people to look at each other, slightly bemused, and say, 'Where did they find a real centaur to play that role?' "

But Gresham knows that many viewers will dissect the movie's theology, even more than its production values. They will be especially tense when the Christ figure in Narnia, the lion Aslan, offers himself as a sacrifice.

In a lengthy speech after his resurrection, Aslan explains that the evil White Witch "knew the Deep Magic. But if she could have looked a little further back ... she would have known that when a willing victim who had committed no treachery was killed in a traitor's stead, the Table would crack and Death itself would start working backwards."

This is, as Time magazine noted, "Christianity in a kid-lit veil."

"They can change a speech like that a little. They may need to shorten it," stressed McCusker. "If they stay true to the spirit of what was written, people will understand what is happening. ... Lewis has woven the Christian symbolism so tightly into the story that you can't cut it out without changing the story itself. The people who love this book are simply not going to let that happen."