Entertainment

AGE BEFORE BOOTY

SET in an alternative universe in which Zac Efron can grow up to become Matthew Perry and abortion doesn’t exist, “17 Again” makes the ’80s comedies on which it’s modeled seem positively cutting-edge by comparison.

This laugh-starved twist on “Big” and the many lesser body-swapping comedies of the era is basically a lecture on sexual abstinence. It’s aimed at the tween girls who idolize the squeaky-clean Disney star, as well as their aging Gen X parents who grew up on those movies.

As if.

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Back in 1989, Efron’s Mike abandons his dreams of becoming a college basketball star when he learns his girlfriend, Scarlett, is pregnant.

Twenty years later — Mike is now Perry and Scarlet has grown up to become the embittered Leslie Mann — the couple is divorcing. He’s a sad-sack pharmaceuticals salesman (cue erectile dysfunction jokes) who’s alienated from their son and daughter, both now in high school.

Through the intervention of a magical janitor (Brian Doyle Murray), Mike gets reverted to his teenage self (Efron) for another shot at hoop stardom. But wouldn’t you know it, Mike finds he is more interested in winning over his estranged wife and helping the kids.

Although there were appreciative yelps in the tween-packed audience when he appeared shirtless, Efron is not exactly this generation’s Michael J. Fox. The closest he comes to actual acting is in a dancing scene with Mann.

There is a fairly bizarre — horrifying, if you actually think about it — sequence in which the newly teenage Mike gets the girls in his high school class to spurn the offer of free condoms in favor of a chastity pledge. But director Burr Steers, who directed the deeply subversive “Igby Goes Down” seven years ago, carefully stays away from anything too interesting in his first feature gig since that flop.

For a few minutes, it seems like Mike’s son — played by a sexually ambiguous newcomer named Sterling Knight — might have the hots for the teenage Mike, whom he doesn’t realize is his father. But Mike quickly hooks up the son with an “available” girl at the same time he’s trying to separate his daughter (Michelle Trachtenberg) from her trashy boyfriend who wants to go All The Way.

The daughter’s subsequent attempt to unwittingly seduce her father doesn’t get very far, although Mike does have to defend his understandable reticence — and his “very tight” jeans — with the requisite “I’m not gay” speech.

Mann does what heavy lifting there is, trying to convince the audience that Efron and Perry (who, thankfully, has very little screen time) are actually the same person at different ages. Most of the laughs are generated by Thomas Lennon as Mike’s billionaire, memorabilia-loving buddy, who is persuaded to pose as Mike’s father when his pal re-enrolls in high school.

It’s hard to say what’s funnier, Lennon’s frosted comb-over-and-under, or his twisted courtship of the high school principal (Melora Hardin), which reaches its high point with a conversation in Elvish.

“17 Again” is the sort of movie where you take your pleasures where you can find them.

lou.lumenick@nypost.com

17 AGAIN

Rearrested development.

Running time: 95 minutes. Rated PG-13 (mild profanity and sexuality). At the E-Walk, the Lincoln Square, the Chelsea, others.