“A Good Old Fashioned Orgy” is a sex romp that flops around more than it romps.
But at least there’s plenty of sex, right?

Well, yeah — a bit of full frontal nudity and a heaping helping of copulation. But there aren’t a lot of laughs from some not very interesting or empathetic characters in this comedy about eight friends who plan and carry out a party that is to be a ’70s throwback, a partner-switching soiree to commemorate all the good times they’ve had at their weekend house in the Hamptons.

Jason Sudeikis is often the over-the-top wingman of comedies like this (“Horrible Bosses,” “Hall Pass”). He’s a bland “lead wolf” in this pack. Eric is the 30ish office worker whose weekend escapes to his dad’s getaway in Sag Harbor include epic parties that he plans and throws. One such epic — “The White Trash Bash,” complete with mullet haircuts, lawnmower races, livestock and “pregnant” women getting plastered.

“I’m sorry if I got beer on your baby!”

Then Dad (Don Johnson) decides to sell this spacious weekend getaway. More cash to play around with his latest trophy girlfriend.

Eric and seven of his closest friends ponder ways to sabotage the Realtors — Lin Shaye (You KNOW there’s going to be inappropriate little old lady sex if the “Something About Mary” granny is on board) and Leslie Bibb. And resigned to losing the place, they ponder ways to send it out with a bang.

“An orgy!”

“People don’t HAVE orgies!”

“They USED to!”

This comes in the context of an unfunny conversation about how AIDS robbed their generation of the free sex ’70s, and how “kids today” have their own brand of promiscuity. Eric has most of these conversations with his pal, McCrudden, played by Tyler Labine in a faint imitation of the Early Jack Black.

Orgies were most famous for being amongst strangers — coke and booze-addled strangers. But these folks don’t know that. Will the women in their circle go for it?

“Insane, idiotic and self-destructive,” complains relationship counselor Alison (Lake Bell). But when Laura (Lindsay Sloane) and Sue (Michelle Borth) see it as a way to finally sleep with Eric or Adam (Nick Kroll), it’s game-on.

The TV writers turned writer-directors for the film, Peter Huyck and Alex Gregory, concoct a few scenes of “research” (Eric and McCrudden drop in on a “swingers” club that meets in a mattress warehouse, after hours) which have a laugh or two. They work in a subplot of the newly-married couple (Lucy Punch and Will Forte, funnier than the leads) who are excluded from the orgy, and the writers try to make relationship-phobic Eric have second thoughts as he takes up with the lovely real estate agent played by Bibb.

But that doesn’t work. None of the stuff supposed to give this “heart” works. The indecisive would-be rocker (Martin Starr) and his anything-to-make-you-happy girlfriend (Angela Sarafyan) are undeveloped, the girlfriend bonding moments have an unreality to them, the inevitable girl-on-girl scene is just frat-boy fantasizing.

And Sudeikis, forced to hold all this together and render it plausible, loses his “wingman” swagger. He’s usually the guy who riffs with the leading man and finds comic gold in semi-improvised banter in just a few scenes. In “Orgy,” there’s nobody funnier for him to riff off of, and too many one-liners tumble to Earth like wounded ducks.

I did like David Koechner, who shows up as a bearded sage of the swinger scene — pervy, nervy and leadership savvy.

“If you don’t run, nobody behind you will run,” is his advice for keeping the orgy-reluctant in line.

The sex sequences are revealingly awkward — with their “Don’t try this at home” message. But without characters we can invest in, this “Hangover Meets Zack & Miri Make a Porno” is just the “porno,” and entirely too tame for that, too.

MPAA Rating: R for pervasive strong sexual content, graphic nudity and language

Cast: Jason Sudeikis, Leslie Bibb, Lake Bell, Lucy Punch, Tyler Labine, Will Forte.

Credits: Written and directed by Alex Gregory and Peter Huyck. A Samuel Goldwyn release.

Running time: 1:41