Seth Rogen, Zac Efron and Rose Byrne certainly don't seem to belong anywhere near the conversation of great cinematic comedy trios, but that oddest of casting mismatches makes a bawdy splash in the genre with Neighbors, a raunchy comedy of intergenerational warfare that's destined to become an instant comedy classic.

That’s right, even Rose Byrne, one of the least approachable actresses in the business, gets in on the antics by channelling her one-off Bridesmaids funny as Kelly Radner, wife to Rogen’s Mac. The couple are newlyweds with a young child and a new house trying to enjoy the American dream before that fleeting marital bliss gives way to middle-aged drudgery.

Though they haven’t quite given up on their 20-something coolness, the strains of adulthood begin to take a toll when Mac and Kelly discover their new next-door neighbors are a rowdy bunch of Delta Psi Beta fraternity brothers led by Efron’s hunky Teddy Sanders.

While the casting of Rogen was a given -- the role was actually written with him in mind -- it’s Byrne and Efron who are director Nicholas Stoller’s secret weapons here. I can’t recall much more than even the tiniest of endearing smiles from Byrne in any of her roles before and since Bridesmaids, and Efron has struggled to shed his High School Musical schoolboy innocence. But here, they are both inspired choices that elevate the film. As odd as it may sound, we’ve possibly found a couple of new comedic go-tos in Byrne and Efron.

Byrne not only keeps up with the seasoned Rogen, but actually manages to wrest a few scenes away from him. She’s never afraid of putting herself in a compromising position to get a laugh and can throw the filth with the best of them.

Efron makes us forget his unremarkable turn in this year’s abysmal That Awkward Moment. Even though he can’t help cavorting shirtless to flex his pecs in Neighbors, there’s a secondary level beneath his character as he morphs from a completely unlikable douche bag of a character, to a totally relatable and charming neighbor motivated by the family he has created within his fraternity.

Mac and Kelly try to play along and make the best of the awkward situation, even going so far as to turn their ball caps around, brush up on their daps and bro-hugs to introduce themselves as the cool neighbors. But as the parties continue to grow more and more epic, both sides dig in to defend their own side of the picket fence.

But declaring war with their frat-house neighbors turns out to be a tragic mistake as the two parties wage a relentless battle of sabotage and one-upmanship that threatens to either get the frat boys kicked off campus or make the newlyweds lose what’s left of their sanity. Most of the film’s best moments come from these comedic shenanigans that are brilliantly funny but never mean-spirited.

Writers Andrew J. Cohen and Brendan O'Brien take a page from the Apatow playbook and infuse their raucous comedy with just enough human emotion and warmth of heart to offset the near relentless onslaught of profanity, nudity, and raunchy sight gags. Strangely, it only takes ten minutes of the former to offset the one-hour-plus of the latter, but regardless, that ratio works perfectly here. Plus, the writers take full advantage of the wonderful intergenerational irony born from the idea of a thirty-something being the older guy who yells at the 20-year-old to keep the noise down. Growing up will do that to you, as will a newborn in the family.

You’ll want to visit Neighbors more than once. It’s a delightful story about growing up and learning how to say goodbye to youth as the responsibilities of adulthood begin to set in. Wait a minute. Forget that. It’s just an hilariously dirty romp through a gutter of funny moments and filthy sight gags delivered by the most unlikely of comedic threesomes. While most of the comedic gags work, even the ones that don’t never cause Neighbors to overstay its welcome.

(Released by Universal Pictures and rated “R” for pervasive language, strong crude and sexual content, graphic nudity and drug use throughout.)

Review also posted at www.franksreelreviews.com.