Grade: B+

Verdict: Jennifer Garner gracefully graduates to movie stardom.

"13 Going on 30" bounds on-screen with the same sunny confidence its star, Jennifer Garner, conveyed as she strode across the Oscar stage in February in that incredible dress. And it could well give Garner the kind of career bounce "Pretty Woman" gave Julia Roberts.

A gender-bended "Big" with a "Sex and the City" gloss, the movie begins in 1987 when bright, gawky Jenna's (Christa B. Allen) 13th birthday party is ruined by some despicable junior-high bullies who call themselves the Six Chicks. Her best pal, a chubby aspiring photographer named Matt (Sean Marquette), tries to comfort her, pointing out she's much more imaginative than those dumb snobs. "I don't want to be imaginative," she wails. "I want to be cool."

And thanks to some magic wishing dust (plot strain ...), she is. Jenna wakes up the next morning 30, flirty and looking just like Garner. She also has a famous boyfriend who plays for the New York Rangers; a former Six Chick, Lucy (Judy Greer), as her best friend; and a job as the editor of her favorite magazine, Poise.

But inside, she's still an insecure kid who gets the willies when her boyfriend walks around the apartment in the nude and who thinks she can hail a cab with a timid "Excuse me?"

And she has no idea what that strange sound in her purse means (no cellphones in 1987).

Overwhelmed by it all, she tracks down Matt (Mark Ruffalo), who's grown up to be a very cute and very successful photographer. She learns from him they haven't been friends for years because, to get where she is, she's been a cold, manipulative rhymes-with-witch.

Pretty in pink, green, red and every other color you can think of -- she changes outfits about every six minutes -- Garner is simply radiant. Plus she deftly nails Jenna's essential childishness, whether she's sharing a pajama party with some real 13-year-olds or dressing down Matt by telling him, "You're mean and rude and sloppy and frizzy."

Of course, Ruffalo ("You Can Count on Me," "Eternal Sunshine of the Spotless Mind") is anything but. He's become one of the few actors who can make gentleness sexy. Greer, who slightly recalls Anne Heche in appearance and style, is excellent as the conniving "best friend." And Andy Serkis is also in fine (and human) form as Jenna's boss -- yes, that's Gollum in a goatee.

Big Apple stress, boy stress, shoe stress (which pair to wear?) -- it's what the "Sex" girls dealt with weekly.

And that's what separates "13" from this spring's other cute-girl movies, "Ella Enchanted" and "The Prince & Me." Not only will every female between 13 and 30 (and above) want Jenna's clothes, jewelry and hair doo-dads, but the humor is more adult and the tone less fairy-tale-ish. Early in her transformation, when a bewildered Jenna says incredulously to Lucy, "You're really my best friend?" Lucy concludes, without skipping a beat, "You're pregnant!"

Just like Carrie and the gang.