It's 1987 and the only thing cute-but-slightly awkward Jenna Rink (played by Christa B. Allen as a girl) wants for her 13th birthday -- besides a date with Rick Springfield -- is to be cool. But when the popular girls ruin her party she finds herself wishing to leave her teenage angst behind and just be 30 instead. Zap! The next morning Jenna (now Jennifer Garner) wakes up in 2004 having skipped over the last 17 years and landed plunk in the middle of her dream life: fancy Manhattan apartment closet full of designer clothes plum executive editor job at fashion magazine Poise. But it doesn't take 13-year-old Jenna long to discover that her 30-year-old self isn't a very nice person. With the help of childhood best friend Matt (Mark Ruffalo) -- who was unceremoniously ditched long ago in Jenna's pursuit of popularity -- Jenna does her best to navigate the challenges of her new life and fix the mistakes she can't remember making. Every week on Alias Garner proves that she's both an able dramatic actress and a champion butt-kicker gamely juggling complex plots and bullet-ridden action scenes. She's even done amnesia -- this season her character woke up in an alley and discovered that she'd lost the last two years of her life. All of which seems to have been excellent preparation for 13 Going on 30. Not only does Garner throw herself wholeheartedly into the film's physical comedy sequences (the "Thriller" scene is of particular note) but she also makes Jenna's initial confusion about -- and gradual delight with -- her new life completely believable. Like Tom Hanks in Big Garner is wholly convincing as a kid stuck in a grown-up's body; her earnest wide-eyed expressions and gawky movements ring true. Ruffalo has an understated appeal as Matt the hipster photographer whose inner fat kid is still insecure and very afraid of having his heart stomped on again. He makes Matt's gradual warming to Jenna's mix of helplessness and sunny optimism seem inevitable. Judy Greer is perfect as Jenna's two-faced friend Lucy and Andy Serkis (that's Gollum to you) who plays Jenna's boss Richard is like a hyper more dapper version of Rowan Atkinson's Mr. Bean. Gary Winick must have known from the minute he signed on to direct 13 Going on 30 that comparisons to Big would be inevitable. And rightly so -- the two films have a lot in common from magical wishes that transform adolescents into adults overnight to ultra-competitive businesses that are transformed by the main character's innocent enthusiasm. What sets 13 Going on 30 apart is that a huge part of Jenna's life has passed her by; unlike Big's Josh whose surroundings stay more or less the same while he changes Jenna has to cope with both a new body and 17 years' worth of memories she doesn't have. That difference offers Winick the opportunity to play up one of the movie's most entertaining themes: '80s nostalgia. The MTV generation is going to get a huge kick out of the opening act's 1987 setting (side ponytails and bright colors galore) not to mention the mostly-'80s soundtrack. Almost as fun -- from a props perspective anyway -- is seeing Jenna incorporate '80s fads like Trapper Keepers into her 30-year-old life. It's that kind of detail combined with a lively script by Cathy Yuspa and Josh Goldsmith that only occasionally strays into cheeseball territory (Jenna's big presentation at work almost crosses the line several times) that makes 13 Going on 30 that rarest of things -- a genuinely sweet truly entertaining Hollywood romantic comedy.