"13 Going On 30," an impishly shallow movie about shallowness itself, concerns an awkward, unpopular teenage girl who wishes herself 17 years into the future so she can enjoy the life waiting for her — that of a cynical, 30- year-old magazine editor (“Alias" megababe Jennifer Garner) with a designer nose job. Lessons are learned, mistakes are magically hosed away.

Hosed, too, is the audience, by a crude torrent of clichés and half- humored scare tactics designed to convince us that prom queens are evil, career ambition is dangerous and media professionals are godless opportunists who take Christmas at St. Barts. Not that we expect more from director Gary Winick, whose debut feature, "Tadpole," took the same crass, pandering approach to the middle-aged feminine libido.

With uncredited movie plagiarism the current norm in Hollywood (see "Johnson Family Vacation," "Connie and Carla," etc.), it seems almost gratuitous to call attention to the fact that "13 Going On 30” steals most of its best ideas from Penny Marshall's "Big" (1988). Still, the comparisons can't be helped, especially when the girl-woman in question, Jenna Rink (Garner), proves her corporate mettle by leading her colleagues in an impromptu dance floor recital of Michael Jackson's "Thriller" video. Childish abandon is the thing that defines today's up-and-coming executive, just as Tom Hanks once discovered by dancing on a toy piano.

While the "Thriller" sequence — for all its perfectly choreographed goofiness — makes us smile, there isn't much else in "13 Going On 30” that does. Jenna, though initially thrilled to find her adult self calling the shots at Poise magazine, predictably becomes distraught with the life she built, one fraught with dishonesty, lust and emotional isolation. And it all started when she started hanging out with the "popular" girls, including Lucy (Judy Greer from "Jawbreaker"), a conniving blonde high school sidekick who, in a wishful and asinine twist of fate, became her co- editor at the magazine.

Essentially, "13 Going On 30” is aesthetic fascism masquerading as open-mindedness, expressed best in the character of Matt, the dorky but devoted childhood friend who Jenna rejected in favor of the popularity fast-track. Played in his adult form by Mark Ruffalo (“Eternal Sunshine of the Spotless Mind"), Matt's superior character is closely tied to his taste in music (he listens to Talking Heads; the other kids like Belinda Carlisle) and movies (we later see a "Blue Velvet" poster hanging in his apartment). The irony in all this is that Matt, were he a real person, would loathe "13 Going on 30” with every fiber of his Talking Heads-listening, "Blue Velvet"-watching being.

Naturally, Jenna makes it her mission to rectify her childhood mistakes and win back Matt (now a handsome photographer) and everything flushes out in perfect fairy-tale fashion. Given a chance to do it all over again, Jenna rids herself of her most crippling character defects, but — in an apparent oversight by the filmmakers that speaks volumes about their lack of sincerity and focus — gets to keep the nose job.

‘13 Going On 30’
Starring: Jennifer Garner, Mark Ruffalo, Judy Greer
Rating: PG-13 (some sexual content, brief drug references)
Playing: Opens Friday at theaters Valleywide Running time: 98 minutes