The exotic, antic ground that "Nanny McPhee" treads has been well-traveled by such diverse products as "Beetlejuice," "Willy Wonka and the Chocolate Factory" (both versions), "James and the Giant Peach," "The Witches" and, most especially, "Mary Poppins." While this adaptation of Christianna Brand's deadpan "Nurse Matilda" series of books may not quite stand at the same level with such impressive predecessors, it's still a spicy little pastry with just the right proportions of flakiness and gooeyness.
Among the movie's small but welcome dividends is having Emma Thompson not only writing the script but pouring the full measure of her witty, borderline-wicked self into the title role: a sort of Mary Poppins with fangs -- or, more accurately, warts and a protruding tooth. You're so glad to see Thompson being funny on screen that you welcome the movie's running gag in which she unexpectedly materializes in a room, explaining dryly to her fretful employer Mr. Brown (Colin Firth), "I did knock."
Nanny McPhee materialized in Mr. Brown's life as a last resort in controlling his seven smart-aleck children, who have found ways to drive away 17 nannies through vile mischief. (They once pretended to have cooked and eaten their baby sister.) The widowed Mr. Brown, a doting if clueless parent, enjoys custody of his unruly brood through the financial support of his great-aunt Adelaide (Angela Lansbury), who warns that if he doesn't marry within the month, he'll go to debtor's prison and the kids will be scattered to various workhouses. (This is set, after all, in Victorian England.)