Nanny McPhee-quel

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The question: When will Emma Thompson get around to making asequel to “Nanny McPhee”? The answer: When pigs fly.

But, as Eleanor of Aquitaine promised in “The Lion inWinter,” there is “pork in the treetops” in “Nanny McPhee Returns,” whichtransplants Thompson’s devious disciplinarian to the British countryside duringWorld War II, a device that allows the star and screenwriter to incorporate abit of “Bedknobs and Broomsticks” — Nanny even has a motorcycle — into thestory.

As in the original, Thompson ties together slapstick andsentimentality as she introduces the overwhelmed Isabel Green (MaggieGyllenhaal, equipped with a respectable accent and an assortment of well-wornhousedresses), a mother of three who’s at sixes and sevens, thanks to wartime shortages,demanding kids, a failing farm and the pressures of managing a shop in whichher elderly, energetic and utterly inept assistant (Maggie Smith) regularlyruins the merchandise. Isabel’s husband is off fighting somewhere, but hisdreadful brother, Phil (Rhys Ifans), is uncomfortably close at hand, pressuringIsabel to sell her property in order to pay off his gambling debts.

On top of everything else, Isabel must now contend with avisit from her niece Celia (Roie Taylor-Ritson) and nephew Cyril (Eros Vlahos),a pair of posh city-raised snobs who call her home “the British Museum of poo”and quickly instigate a little war of their own with Isabel’s children.

The frenzied first half-hour of “Returns” (released overseasearlier this year as “Nanny McPhee and the Big Bang”) sets up this sadsituation with the broad overacting and exaggerated silliness of a Britishpantomime show.

When Nanny (Thompson, obscured by warts, moles and asnaggle-tooth) arrives on the scene to tame the unruly kids and give a bit ofhope to the helpless Isabel — “I’m a wartime nanny: I’ve been deployed,” sheexplains to Isabel — the movie’s tone becomes more whimsical, as if “MaryPoppins” had been rewritten by Monty Python. Mary Poppins had a parrot as asidekick, but Nanny is stuck with a pesky crow named Mr. Edelweiss, who’ssuffering from “the collywobbles.”

While there are occasional notes of seriousness inThompson’s screenplay (particularly in Ralph Fiennes’ chilly cameo as Cyril andCelia’s starchy father), most of its messages are couched in comedy orsurrounded by flights of fantasy. In keeping with the mid-1940s setting,“Returns” features a delicious tribute to swimming star Esther Williams, anoff-course UXB (“unexploded bomb,” Celia explains), and a pair of curvy flirtswho wear the same peroxide-blonde hairdos sported by Barbara Stanwyck in“Double Indemnity” and Lana Turner in “The Postman Always Rings Twice”;unsurprisingly, they turn out to be up to no good.

And yes, that airborne swine makes an appearance as well, provingconclusively that Nanny McPhee will go to any lengths to teach a lesson — or toget a laugh. Happily, she often succeeds on both counts.