On the other hand, we tend to be wary of happiness when it stays. Personal experience demands a certain level of distrust for anything that doesn’t sour. Butter might go bad after a month or two, but there’s a reason why people are suspicious of margarine. There’s a reason why nobody wants to sit next to that guy who’s smiling to himself on the subway. There’s a reason why Tom (Joel McHale) and Janet (Kerry Bishé) — a cartoonishly attractive married couple whose honeymoon phase has just entered its 14th year — make everyone else in their Los Angeles friend group so uncomfortable. Jealousy is one part of it, and the fact that Janet can’t sit through a double date without giving Tom a hand-job under the restaurant table is probably another, but the root of the problem runs a bit deeper.

The social contract relies on an unspoken agreement that bliss is meant to be borrowed and not kept, sold but never owned, and most of us can only survive without it due to the shared understanding that everyone is actually as miserable as we are. This isn’t anything you don’t already know firsthand, and yet BenDavid Grabinski’s giddy debut is so much fun because — and not in spite — of its Serling-like literalness. A clever, high-concept dark comedy that uses the moral clarity of “The Twilight Zone” to see through the veil of modern cynicism, “Happily” jackknifes into the murky waters between #RelationshipGoals and #BodySnatcherVibes as it skewers the assumption that something must be very wrong with anyone who’s too happy for too long.  And it does so by taking that assumption at face value. “They’re pod people,” someone cracks about Tom and Janet, and Grabinski’s propulsive script gives us plenty of reasons to believe them. Even after more than a decade together, Tom and Janet are still so horny for each other that they can’t help but have sex in the bathroom at a houseparty… and again when they get home. “I guarantee that those people are just as miserable as everyone else,” a rubbernecker insists — cut to: some very sweaty proof that they’re not. “Happily” effectively uses sex as an overbroad stand-in for all manner of marital bliss, but the movie’s bat-out-of-hell pop flash (complete with spiritual nods to the likes of Walter Hill’s “Streets of Fire”) and ensemble-driven satirical bite allow it to skim along the surface without selling its ideas short. If character runs a distant second to circumstance here, Grabinski cannily still gets us to root for two people who we’d probably hate on principle in real life.

When Tom and Janet are revealed to be some kind of glitch in the matrix, we blame the matrix. And when Stephen Root — cosplaying as Frank Langella’s role from “The Box” — shows up at Tom and Janet’s door with an injectable serum that will make them resent each other like a “normal” married couple, we’re thrilled that Janet impulsively bludgeons him to death. That murder will become a secret that our prom king and queen will have to keep from their powder keg of a friend group during a weekend getaway at an ultra-sleek AirBNB, as the only two people who’ve never had to perform their happiness suddenly find themselves in the unusual position of having to keep up appearances. It’s a busy premise that soon raises more wrinkles than “Happily” is able to iron out — the Bond-worthy gun arsenal at the AirBNB is a red herring in a film where too many things are already fighting for attention — but the movie is at its best whenever its characters try to act like everything is perfectly smooth. Each of the couples who signed up for this nightmare weekend have their own problems, but all of them are contributing to the shared denial that their relationships are a sitcom and not a horror film, a tension that Grabinski satisfies by splitting the difference between those two modes. That lie starts with Tom and Janet, who tell themselves “we’re not the weird ones, this is the way marriage is supposed to be” with the shakiness of two people whose faith in that idea has just been rattled for the first time, and it trickles down through the rest of the mansion from there like water overflowing from the second-floor shower where they’re obviously having sex even as they argue. “Happily” never lets us doubt that Tom and Janet are great together, even if it’s easy to appreciate the logistical difficulties of being friends with the kind of people who’d (solemnly) dry hump each other during your mother’s funeral. A ’40s noir actor in an Abercrombie & Fitch model’s body, McHale has never been more dimensional in a movie, while Bishé — who should be a household name by now — radiates enough charisma to convince you that every casting agent in Hollywood has been asleep at the wheel for the last 10 years. Grabinski assembles a killer cast to fill out the other rooms in the house, with power-hitters like Shannon Woodward, Paul Scheer, Natalie Morales, and a thankless Breckin Meyer fleshing thin sketches into something more as they cement the mutual hostility that holds this friend group together in its death grip; Natalie Zea is the only supporting actor who’s asked to stand out from the chorus, and she’s fabulously bitter as the ex who’s determined to seduce Tom in order to prove that he’s not as happy as he seems.

As much as these characters might have benefited from more screen time, “Happily” already loses some of its thrust by splitting its attention between insecurity and resentment. Whereas most versions of this movie would reduce Tom and Janet to mysterious objects for the protagonist to spitefully measure themselves against, Grabinski’s film is such an off-kilter delight because it flips the script and tells this story from the perspective of the enraptured sickos who’ve got it all — whose life together is so perfect that even a brief spat over a breakfast omelette is weird enough to sweep through their kitchen with the eerie unease of a giallo film. That “Happily” drifts away from Tom and Janet during its busy second act feels like a missed opportunity, even though the movie finds its way back to them by the end. But the genius of “Happily” — and the reason why it coheres into such a uniquely promising debut — is that Grabinski maintains the courage of his characters’ convictions even when Tom and Janet are struggling to do the same. Slick and entertaining as it is from the moment it starts, “Happily” doesn’t need you to like it, which is precisely why so many people will. It’s rare to see a first movie that’s so broad and personal at the same time, or a comedy of any stripe that’s so palpably enamored by the filmmaking process, but to watch Grabinski’s debut is to be in the hands of someone who knows what they’re doing and knows why they’re doing it. From throwaway gags that make us feel like we’re laughing at someone else’s inside jokes (yes, you heard that “Stealth” reference correctly), to note-perfect needle drops that fall into place with a fated sense of purpose, and a precise compositional design that always feels intentional yet never over-determined, “Happily” is eager for your attention, but secure enough in its own identity not to require your approval. The love that Grabinski’s movie reflects for the movies that Grabinski loves (and for the experience of making his own) is every bit as pure and worth preserving as the happiness shared between Tom and Janet, and there isn’t a damn thing wrong with that.

Grade: B

Saban Films will release “Happily” on VOD on Friday, March 19. Sign Up: Stay on top of the latest breaking film and TV news! Sign up for our Email Newsletters here.