You saw the trailer, and you figured you were probably in for a latter-day "Big" with a female lead and less brains. And you were right. But what you couldn't have anticipated is how foggy the movie's memory is: When we first spy suburban washout Jenna Rink at the age of 13, the year is supposedly 1987 -- yet she's madly in love with Rick Springfield and has memorized the choreography to "Thriller." The easy guess is that the action must be taking place somewhere in Eastern Europe, but no passports are mentioned when Jenna wakes up in a Manhattan apartment one morning, transformed into a "30, flirty and thriving" magazine editor. The idea that she's grown up overnight while everyone else has done it the hard way proves far less comedically fertile than "Big's" mirror scenario. Yet no matter how awkward the movie often is -- and make no mistake, that scene of the older Jenna clutching her boobs in delight is intended to afford all the fun of pedophilia without any of the guilt -- it's also gently beguiling on occasion, thanks mostly to the gum-snapping effervescence of star Jennifer Garner. Either she's one terrific actress or it's just her natural state of being to behave like a 13-year-old. We'll let you know as soon as we can find out for sure.