Garner goes from tough to fluff

As Sydney Bristow on ABC's Alias, Jennifer Garner is a hard-as-nails, butt -kicking machine working for the CIA. She spends countless hours whipping both her acting skills and martial arts moves into shape to give life to her embattled character.

As Jenna Rink in 13 Going on 30, Garner transforms herself into a happy-go-lucky, but very confused13-year-old who gets warped into the fast-paced world of adulthood.

And she has a lot of fun doing it.

Garner establishes herself as a versatile actress as Jenna and makes this all too predictable tale reminiscent of Big, a cute and funny film. There's not a trace of Bristow in Garner's wide-eyed, perplexed Jenna. Instead, we see a happier, more innocent side of the actress.

When we meet her, young Jenna (Christa B. Allen) has just been inducted into the world of bra-wearing, fashion-conscious teenagers and wants nothing more than to celebrate her coming-of-age with the cool Six Chicks, the most popular girls in school. To do so, she shuns her best friend Matt (Jack Salvatore Jr.) when the girls come to her party, and later rejects him when he tries to console her after Jenna realizes that the Six Chicks tricked her into waiting blindfolded in the closet while they took off. Jenna runs back into the closet, crawls into a corner and subsequently wishes that she were a cool, confident 30-year-old, like the ones she admires in Poise magazine.

In the morning, Jenna wakes up in a king-sized bed in a large New York apartment, complete with bills to pay, a scantily clad boyfriend ("You're naked!" Jenna exclaims) and alas – breasts! How did I get here, she wonders, and how do I get home? Jenna races out of her apartment and is greeted by her friend Lucy (Judy Greer, What Women Want), who tells Jenna that she is now a "big time magazine editor" at Poise.

Desperate for some clarity, Jenna finds an engaged Matt (Mark Ruffalo, Eternal Sunshine of the Spotless Mind), who, in between Jenna's frantic raving about her current situation, explains that Jenna grew up to be a snotty Six Chick, ruining their friendship. Jenna recognizes that her affiliation with the popular girls has turned her into a malicious and conniving character, someone she does not want to be.

Without the casting of Garner in the lead role, this movie would have fallen flat. The story has been told time and time again, and viewers can predict the ending just by glancing at the trailer. But Garner brings originality to the movie, partially because she is a good actress and partially because she imbues her own personality into the role. We could have done with a few less exasperated gasps and puzzled expressions, but otherwise, Garner plays a 13-year-old to perfection.

Jenna's obvious confusion over the very different world of 2004 versus 1987 is also especially amusing. When her cell phone rings in her coat pocket, she scrambles around, her eyes searching the skies, crazily asking Lucy, "Do you hear that sound?" Later, her assistant tells her that "Eminem needs a decision now!" and Jenna replies, "Plain! Peanuts!"

13 Going on 30 isn't the most original movie. But you can't help thinking, as Garner shimmies to Michael Jackson's "Thriller" or leaps off of the swings like a child, that she is having the time of her life. The core of this movie is Garner's experience, and it sure is fun to watch.

13 Going on 30 is rated PG-13 for some sexual content and brief drug references.