Jason Statham

"If only I could go back to high school with what I know now."

It's a commonplace adult fantasy, and 37-year-old Mike O'Donnell gets to live it in a semi-successful new body-swap comedy called "17 Again."

As a high school senior in 1989, Mike was on the verge of a college basketball scholarship when his girlfriend, Scarlett, revealed that a little O'Donnell was on the way. Mike nobly gave up college for marriage, fatherhood and thankless work.

Twenty years later, he's disappointed in his job, scorned by his kids and about to be divorced by Scarlett (Leslie Mann), whom he blames for his misfortunes.

It's at this point that Mike (through a remarkably lame special effects sequence) gets to be the mother of all oxymorons: a 17-year-old with good sense. Posing as a transfer student called Mark, he re-enters high school and sets out to right the wrongs of his youth. His own daughter and son are among his clueless classmates.

Mike is played by Matthew Perry as an adult and by Zac Efron as the younger model. This demands a big-time suspension of disbelief on the part of viewers, as the two actors are as visually dissimilar as Woody Allen and Tom Cruise. The unlikely transformation doesn't seriously damage the movie, however. If we can accept the notion of a body switch, then perhaps it's no big deal for Perry to turn into Efron.

Mike uses the chronological regression wisely, counseling his classmates against pre-marital sex and advising young women to respect themselves so that they will be respected by testosterone-charged boys. He also learns to accept responsibility for his actions and not to take loved ones for granted.

There is a fitful, not-quite-finished feel to the movie, but director Burr Steers does keep it moving at a lively pace. He's helped by Jason Filardi's screenplay, which buoys the shopworn premise with occasional shots of wit and navigates inoffensively across awkward moments such as when Mike/Mark is hit on by his own unknowing daughter. The cameras focus primarily on Efron, who's the Hollywood heartthrob du jour thanks to Disney's "High School Musical." Perry, late of "Friends," probably is better known to adult moviegoers. But "17 Again" isn't really aimed at adults.

Credit the filmmakers, too, with casting able supporting actors. Foremost among them is Thomas Lennon, who plays Mike's lifelong friend, Ned. As a wealthy sci-fi geek and determined suitor of school principal Jane Masterson (Melora Hardin), he provides "17 Again" with its funniest comedic scenes.