Sarah Jessica Parker, the 25-year-old who plays SanDeE* (yes, that's how it's spelled), Steve Martin's flaky young fling in L.A. Story, is well known for her masses of untamed curls. But today the petite Parker who even manages to steal scenes from Martin has had it straightened, and even she doesn't seem to recognize herself. ''People identify me by my hair,'' she says, turning her head and watching her locks swing. ''For years I held it over my face so they couldn't see part of me.'' That's definitely unlike SanDeE*, an uninhibited starlet who punctuates every utterance with a goofy pirouette, leaving Martin dizzy with middle-aged desire. But Parker, who lives with longtime love Robert Downey Jr., is much more modest than her performance suggests. Of her comic sex scenes, she says, ''One of the first things I had to do was put Steve's hand on my breast. I thought, 'My hand will be shaking that's the last thing SanDeE*'s would do.'''
Ohio-born and Gotham-raised, Parker spent two years on Broadway in the title role of Annie and by 17 was the brainy ''Beanpole'' on CBS' schoolgirl comedy Square Pegs. At 22 she returned to TV as a flighty newlywed on NBC's A Year in the Life; now she can be seen on ABC's Equal Justice as an assistant DA. But while she's quick to defend a TV career (''I'm able to make house payments, buy clothes, eat out, be frivolous''), she counts on her twirl as SanDeE* to be her film breakthrough. For that she credits Martin. ''Steve allowed me to be so big and broad on screen,'' she says. ''My friends have never seen me like this before.''