Amid all the gross-out humor of ‘Blockers,’ some moments of inspired lunacy

In “Blockers,” Leslie Mann plays Lisa, the single mom of a high-school senior named Julie (Kathryn Newton), a vivacious teenager who, as the movie opens, announces a newfound goal of losing her virginity on prom night.

Julie’s best friends Kayla (Geraldine Viswanathan) and Sam (Gideon Adlon) quickly warm to the plan, agreeing that, as with everything else in their lives, they’ll take the leap together — or at least at the same time. When Lisa spies the trio’s texts on Julie’s laptop, she and the other girls’ dads — played by John Cena and Ike Barinholtz — embark on an anxiety-fueled, hysterically pitched mission to scuttle the young women’s plans, invading the kids’ prom night like a battalion of helicopter parents humming “Ride of the Valkyries.”

As a burlesque of parental angst and sex panic, “Blockers” possesses sharply observed moments of inspired lunacy. Produced by Seth Rogen and Evan Goldberg, this combination of satire and slapstick also includes the requisite number of dumb, gross and otherwise icky sight gags, whether in the form of Cena agreeing to a “butt chugging” contest with a bunch of beer-buzzed 17-year-olds, or some unsettlingly graphic close-ups of male genitalia.

Mann, a gifted comedian given a gratifying showcase for her talents (especially later in the film, when she winds up in a hotel-room-turned-love-nest), makes the most of a role that presents the broadly comedic twin of “Lady Bird,” which also centered on a mom dealing with impending separation by spiraling into terror and misplaced rage.

Directed by newcomer Kay Cannon from a script by Brian Kehoe and Jim Kehoe, “Blockers” suffers from ungainly, choppy pacing. It feels like a slapdash collection of scenes rather than a balloon sent smoothly aloft, with jokes often falling as flat as Cena’s buzz cut (a running gag centers on his tough-guy character’s propensity for crying, a go-to bit that ages fast). There are more than a few stretches when nothing much happens save for getting one group of people to the next backdrop for a sex joke or sight gag (frequently at the expense of a freewheeling couple played by Gina Gershon and Gary Cole).

Still, the underlying values of “Blockers” are refreshingly healthy and affirming, proclaimed not only by Kayla’s pointedly levelheaded mom (Sarayu Blue) — in a fiery speech about the double standards and the dubious politics of policing female sexuality — but by the girls themselves.

Smart, self-aware, comfortable with asking for what they want — and, more important, with refusing what they don’t want — these teen feminists feel like avatars of an age when the term “me too” will have more to do with pleasure-with than power-over. Together with their male contemporaries — Miles Robbins delivers a particularly scene-stealing turn as the mellowed-out Connor, who sports a man-bun and an equally cloying it’s-all-good vibe — the girls of “Blockers” emerge as admirable examples of autonomy, confidence and self-respect, never more so than when their clueless parents are running amok, half-cocked.