13 Going on 30, pegged as the girl version of Tom Hanks’ Big, leaves no doubt that the new, hip career choice for female protagonists is big-shot magazine editor. First Kate Hudson grinned and cooed at a swank New York women’s magazine in How to Lose a Guy in 10 Days, and now Jennifer Garner is playing the lovably dorky fashion aficionado in 13 Going on 30.

In a departure from her role as spokeswoman for Girls Who Kick Ass on ABC’s “Alias,” Garner bounces about onscreen playing a teenager playing a grown-up with enough vibrancy to carry the film’s weaker points.

The 30-year-old flirty and fabulous Jenna Rink is a top editor at Poise Magazine and the lucky lady on the arm of a hot hockey star (Samuel Ball). The problem is, just yesterday she was a 13-year-old wishing her way into adulthood. And 30 is not all it’s chalked up to be.

This shameless chick flick is part teenage angst, part ’80s homage and part tearjerker; at times it seems the film doesn’t know what to do with itself.

The expository scenes of 13-year-old Jenna’s angst, complete with nostalgic ’80s fashion and music, run a bit long but are so sickeningly sweet and fun that they make the over-the-top transition from 1987 to 2004 forgiveable. It’s fun to imagine how Jenna will adjust to her 30-year-old body, complete with breasts, hips and high heels, but as she gets into several precarious adult situations, the fun ends and implausibility sets in.

Beyond the fact that people can’t wish themselves 17 years older and wake up the next morning next to a naked sports star, 13 Going on 30 falls short of believability, as it provides no explanation for Jenna’s transition from ecstatic teenager to in-control adult, nor does it address the serious situations Jenna encounters (sexual pressure, Poise’s financial challenges).

The confused Jenna runs to the first person she can think of – her best friend Matt (Mark Ruffalo), now a struggling photographer.

Jenna learns that what seems a dream at 13 can be a hollow life at 30, as she discovers that, although she’s been popular, a guy magnet and Prom Queen, she has become a shallow, vindictive career woman with no friends.

Can Jenna save herself from this empty life by reclaiming her friendship with Matt?

Well, it’s a romantic comedy, so of course she can. And the audience learns that getting everything they want out of a romantic comedy – including choreographed dance numbers, sappy montages and a fairy tale ending – isn’t always as satisfying as they’d think.

Ultimately, 13 Going on 30 is fun to watch, with plenty of laugh-out-loud moments and tingly nostalgia for anyone who even vaguely remembers the ’80s.

But the film leaves too many questions unanswered and glosses over the seriousness of a 13-year-old being thrust into the adult world by pushing the age issue back as Matt and Jenna’s relationship pushes forward.