It's hell getting old. You're overworked, underpaid, get grey hairs, everything hurts, there's barely time for sex, you fall asleep on the couch watching 'Game of Thrones' and, unless you're George Clooney, you're just not cool anymore. You either hike up your pants and accept it, or you wage all out war. It's the latter that highlights the uproarious Seth Rogen and Zac Efron comedy 'Neighbors,' which just might be the funniest American movie since ... well, since Seth Rogen's last movie.

The film stars Rogen as Mac Radner, who, along with his wife, Kelly (Rose Byrne), has sunk a lot of money into a dream house in a quiet, suburban neighborhood, where they plan to raise their baby girl, Stella. That is until the Delta Psi frat house moves in next door. Despite the noise and disruption, the yuppie couple share an agreement with the frat alpha dogs (Zac Efron and Dave Franco), until they break the code and call the cops in a fit of frustration one night. From there, it's the family vs. the frat in a wildly escalating battle of who can force whom out of the neighborhood first.

While the 'Neighbors' story is slim, the film more than makes up for a flimsy plot with jokes and comic set pieces that come rapid fire and land with such impressive accuracy and success that you're laughing too hard to notice much else. Directed by Nicholas Stoller ('Forgetting Sarah Marshall'), 'Neighbors' is an insanely funny comedy; the kind where jokes are so easily missed because you're still laughing too hard at the one they told just a few seconds ago.

What's most remarkable about 'Neighbors' is its restraint. Compared to Stoller's last film, 'The Five-Year Engagement,' a film that felt as long as its title, 'Neighbors' feels positively brisk. Most modern comedies can't find it within themselves to trim the fat, leaving jokes to go on far too long and killing momentum and timing. There's only one real scene of extended improv and it's one of the few bits that falls flat. Stoller keeps the film moving along with an impressive speed and momentum, never once slowing down and keeping a chaotic and unpredictable tone.

Frantic energy has always been one of Rogen's strong suits and he's at his best here dealing with the increasingly rising stakes in the war with his new neighbors. The more the war next door escalates and chaos piles up, the better Rogen gets. He hasn't been this good, this sharp and this comfortable with his own skills as a comic actor since 2008's 'Pineapple Express.' Rogen has made a living out of playing the listless man-child and some of that is certainly on display here as his character initially would rather smoke a joint with the bros next door than rat them out. But, his character in 'Neighbors' feels different for Rogen, who is playing a role that will appeal more to the weary fathers in the audience than the stoners.

And, if Rogen cements his status as one of the finest comedic actors working in Hollywood, Rose Byrne has all but declared herself more than able to stand alongside any of the best comediennes. Byrne, who played alongside Kristen Wiig in 'Bridesmaids,' proves every bit her equal in a shockingly funny performance that, in a film chock full of funny dudes, steals the show. Previously relegated to supporting roles (including two of Stoller's previous films, 'Forgetting Sarah Marshall' and 'Get Him To the Greek'), this is Byrne's first lead role in a comedy and we're sure it won't be her last. What could've been the generic mom/wife character who stands on the sideline nagging her husband (a stereotype even alluded to in the movie -- "Haven't you see a Kevin James movie?!") transforms as Byrne unhinges as the movie progresses, and both the actress and the character are in complete control.

Efron is impressive in straying far from his usual type, but one wonders how far it is from Efron's actual personality. He's at one point a complete sweetheart, charming all the little old ladies on the block, and the next a sadistic madman, rigging booby traps around the Radner home. He could just be played as a dummy, but Efron wisely plays him as a dummy who is slowly beginning to realize that he's a dummy, even amongst his bros. He can't give up the fight, because he has no idea what he'll do when he does. It's a movie that will certainly help break the former 'High School Musical' star out of whatever creative rut he found himself in, even if comedy isn't always in his future.

While Rogen, Byrne and Efron make up the strong leading roles, Stoller has impeccably cast the rest of the film with a hilarious group of actors ranging from Dave Franco (who deserves a lead role at this point), comedian Hannibal Burress, Jerrod Carmichael and Ike Barinholtz. That's not even mentioning the little baby, who's adorable even by Hollywood baby standards (make sure you stick around after the credits, for a fantastic baby-centric credits sequence).

Right up there with 'This Is the End' and 'Bridesmaids' as one of the funniest films of the past few years, 'Neighbors' is a confident and chaotic comedy that marks career bests for almost all involved. Getting old may be hell, but as this group proves, getting older sometimes means getting better.

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'Neighbors' opens in theaters on May 9.

Mike Sampson is the Editor-in-Chief of ScreenCrush.com.

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