NANNY MCPHEE — * 1/2 — Emma Thompson, Colin Firth, Kelly Macdonald; rated PG (slapstick violence, vulgarity, mild profanity).

Not to give away anything crucial, but the bratty kids in "Nanny McPhee" do eventually warm to their new baby sitter, played by a virtually unrecognizable Emma Thompson.

But it's hard to say whether audiences will warm to the film, which gets more frantic and aggravating, reveling in juvenile humor, dumb slapstick, flatulence and computer-graphics trickery — including a talking baby bit that is more creepy than funny.

Consequently, this charmless comic fantasy is a major disappointment, especially when you consider that Thompson also wrote the script. It's hard to believe "Nanny McPhee" was adapted by the same person who won an Oscar a decade ago for her "Sense and Sensibility" screenplay.

"Nanny McPhee" is based on material from the popular "Nurse Matilda" novels by author Christianna Brand about a widower (Colin Firth) who is having a hard time finding a new nanny, since his brood of seven ill-behaved children has already terrorized 17.

The kids are also making it impossible for him to find a new wife, and his Great Aunt Adelaide (Angela Lansbury) is threatening to cut him off financially if he doesn't remarry.

Help on one of those fronts arrives when Nanny McPhee (Thompson) turns up on the doorstep. Cedric is only too happy to hire this self-proclaimed "government nanny," who appears to have magical powers. At first, the children, led by oldest son Simon (Thomas Sangster), try to run her off like all the others. However, they do become more cooperative over time, and appear ready to mend fences with their harried father.

It's clear that Thompson and director Kirk Jones ("Waking Ned Devine") were trying to make a darker, edgier "Mary Poppins." Unfortunately, all they can come up with are characters who wear goofy-looking noses and other facial appliances.

The only people who will find such things funny are really young children; while adults are bound to be put off by the film's clownish sense of humor and crass elements.

And what a waste of talent, with British veterans Derek Jacobi and Imelda Staunton, who look a little embarrassed, and Lansbury, who has little to do but act haughty.

"Nanny McPhee" is rated PG for slapstick violence (pratfalls, a cake fight), vulgarity (including flatulence), and scattered use of mild profanity (some of it religiously based). Running time: 98 minutes.