To Her, It’s Kids’ Stuff : Movies: Mara Wilson, 7, is earning praise from her co-stars in the upcoming ‘Miracle on 34th Street,’ but acting is just something she says she likes--for now.

CHICAGO —  The most refreshing revelation about Mara Wilson is that in spite of her growing popularity and marketability--due in part to her cuddly performance as Robin Williams’ youngest child in the smash “Mrs. Doubtfire”--she remains a relatively normal, happy 7-year-old.

In fact, she might well be one underage performer W. C. Fields, famed for his unswerving enmity toward child actors, might have tolerated, even enjoyed, as a co-star.

Director John Hughes plucked Wilson from a sea of 1,000 young girls who auditioned for the part of Susan (first played by Natalie Wood in 1947), the unbelieving child who rejects all notions of Kris Kringle in Hughes’ remake of “Miracle on 34th Street,” which is filming here and is scheduled for a Thanksgiving release.

With a voice as breezy as bird song, Wilson takes a break from the set of “Miracle” to play on a toy train idling on a playground a block from her temporary Gold Coast living quarters.

“This is what I call fun ,” she says as she prepares to scale the locomotive, widening her hazel eyes. Eventually, she settles into the driver’s seat and submits to a gracious yet obviously perfunctory interview about acting, her secret passion to write and the highs and lows of her life, thus far.

“I don’t know if I’m always going to be acting. Maybe when I grow up, I will be a scriptwriter. I already have a few scripts in my head,” she says. “But, for now, I like acting, because it feels like I’m pretending. It’s not exactly like playing here, on the train, because when you act, you can’t say what you want to say; you have to say what (the director) wants you to say.”

Such innocent acuity comes as no surprise to her co-star Sir Richard Attenborough, who plays Kringle.

“She is truly marvelous, and the brilliance of somebody like Mara is that her concentration as an actor is absolute; she doesn’t have to think of what her next line is. She awaits her cue and plays her line,” Attenborough says during a break at Hughes’ sprawling indoor studio on the city’s northwest side. “She is a total professional, and I think really it’s because she’s been blessed with fabulous parents.”

Echoing that is Elizabeth Perkins, fresh from her prehistoric jaunt as Wilma Flintstone. Perkins plays Wilson’s pragmatic, career-obsessive mother in “Miracle.”

“What makes Mara so amazing is her mom, Suzie, who is probably the most normal mom I’ve met in a long time. She does not fit the bill of a stage mother at all. She treats Mara like one of her five children.”

Born the fourth of five children to Suzie and Mike Wilson in the San Fernando Valley on July 24, 1987, Wilson was inspired to pursue acting by her oldest brother, Danny, now 15, who had successfully landed a few TV commercials and small film parts.

“At first, we said no to acting,” says Suzie, who accompanies her daughter to the set every day and helps her rehearse. “We told her you don’t always get jobs you audition for, and it’s harder than it looks.”

When Wilson, then 4, showed no signs of relenting, her mother decided to test her daughter’s determination before signing an agent. She gathered the three elder brothers (the family has since added a baby sister, Anna, 1) and put the child through a series of mock interviews.

“We gave all the boys pens and papers and put her through the works. And, when she finished, they would say, ‘That was good, Mara, but you didn’t get the job.’

“She turned to me and said, ‘That’s OK. Can I try for another one?’ ”

Mara Wilson began working in commercials and then added a recurring role on “Melrose Place” as the daughter of a Russian immigrant, as well as a sizable part in the NBC movie “A Time to Heal.” Then came the reading for “Doubtfire,” which proved to be her launching pad.

As for attempting to fill Natalie Wood’s shoes in “Miracle,” Wilson remains modestly open-ended:

“People always ask if I thought I was good in the movie and I say, ‘Well, some people said I was, but really, how am I suppose to know?’ ” she says. “I guess we’ll just have to wait and see.”