Two couples in a parent trap

“Carnage,” the movie adaptation of Yasmina Reza’s Tony-winning comedy of manners, “God of Carnage,” purports to be a satirical skewering of modern-day parenting, its hypocrisies, power plays and smug moralizing.

But in this leaden production – directed in a rare flat-footed outing by Roman Polanski – what are supposed to be transgressive observations about the holy state of parenthood and matrimony instead come across as self-satisfied and shallow as the pieties Reza intends to puncture.

The tiresomeness of “Carnage,” which Reza adapted with Polanski for the screen, isn’t helped by a case of fatally lopsided casting that finally swamps what should be a smoothly coordinated comic sail.

As the film opens, two couples finish up a meeting regarding their sons, who fought earlier in the day. Whereas Christoph Waltz and Kate Winslet easily find their footing as one of those couples – Alan and Nancy Cowan, the prosperous parents of the aggressor in the playground encounter – Jodie Foster and John C. Reilly seem perpetually off balance and ill-matched as Penelope and Michael Longstreet, an activist author and household supplies wholesaler, respectively, whose son took a wallop to the mouth.

Although the Longstreets are clearly aggrieved, they’re masking their distress under layers of well-mannered solicitude as they wrap up their confab with the Cowans, who are on the verge of catching the elevator out of the Brooklyn apartment building when Michael and Penelope insist they stay for a cup of coffee and cobbler. What ensues is a real-time, 80-minute verbal roundelay that includes, but doesn’t end, with a case of spectacular projectile vomiting. » Read more: Carnage