"Neighbors" is funny for all 96 of its minutes, not counting the credits, and it contains the single best sight gag of the year so far. (We’re talking laugh-out-loud funny and then laugh again later, just thinking about it.) It features another strong comic performance by Seth Rogen, who has resisted getting wrecked by success, and it pairs him with Rose Byrne, who turns out to be his comedic match.

But before we talk about those things, a word about the director. This is the fourth winner in a row from Nicholas Stoller, whose previous films are "Forgetting Sarah Marshall," "Get Him to the Greek" and "The Five-Year Engagement." "Neighbors" is the first he didn’t write, but it shares with those other movies the hilarious set pieces, the moments of social embarrassment and an undercurrent of seriousness that grounds and enhances the comedy and allows the actors to create rounded performances.

Even as we laugh at the characters, we feel for them and recognize that the stakes are high. Rogen and Byrne are a young couple with an infant child in an apparently happy marriage, with all their money invested in their nice suburban house. And then the worst possible neighbors move in: a fraternity. Soon their lives are a nightmare of music blasting at 4 in the morning. They can’t sleep and they can’t sell the house either, because no one would buy it.

"Neighbors" is simply but cleverly structured as a series of changing strategies and escalating incidents. Rogen and Byrne are very funny together, playing off each other with such speed and ease that one wonders how that came about. Were there long rehearsals? Was some of the dialogue improvised?

However it happened, the interaction is fresh and one of the movie’s delights. They seem married — a marriage of opposites, but married all the same — him, lumbering and emotional, her, quick-thinking and scheming.

‘NEIGHBORS’ Rated: R Opens Friday

The first strategy they come up with is to make friends with the frat brothers, particularly the president of the fraternity, played by Zac Efron. Once again, a character that could have been designed purely as a comic construct gets a sober undercurrent. The president may be supremely confident and poised on the outside, but Efron plays him as a dark soul beneath the surface, someone blotting out his life terror through nonstop frolic. This doesn’t take away from the laughs, nor does it become an occasion for some unwelcome fake-poignant moment that’s a hallmark of bad sitcoms and sentimental comedy. Instead, it just rounds out the world of "Neighbors," so that when Rogen and Efron face off against each other, you feel that you’re looking at two characters with everything on the line. It’s funnier because it’s more real.

A nice psychological subtlety of the script — by Andrew J. Cohen and Brendan O’Brien — is that the young couple’s battle with the fraternity is coming at an odd juncture in their lives in which they’re realizing that carefree youth is gone and they now must be responsible adults. Going to war with the fraternity may be a burden, but they’re enjoying it more than they realize — and using it to work through this transition.

But that’s all subterranean. Above ground is just a lot of skillfully conceived and executed comedy.