Starring Seth Rogen and Zac Efron. Rated 18A.

Had Neighbors simply played on the horror of an uptight family as it watches frat pledges unloading kegs and installing giant Greek letters onto the house next door, it might not have been so funny.

But new parents and mortgage-holders Mac and Kelly (Seth Rogen and Rose Byrne) are poster children for Gen X and Y, desperately clinging to their youth like they do to their skinny jeans and old concert T-shirts. And that takes the comedy to a hilariously high level. Just watch as the couple practise multiple ways of saying “Could you please keep it down?” so they won’t sound like old farts to the hard-partying frat dudes next door.

It helps that director Nicholas Stoller never satisfies himself with toga-party clichés, ratcheting up the 24/7 ragers to surreal, bonged-out heights. At one point, a daytime Robert De Niro–themed party spills out onto the lawn right outside Kelly and Mac’s living-room window, so that drunk versions of Travis Bickle and that sociopath from Meet the Fockers are gawking in while they play with their baby.

Zac Efron has found his perfect character here, part sinister asshole, part insecure poser as the frat leader. And a surprisingly game Byrne has fun with a much more active, foul-mouthed role here than women usually get in these sausage fests. Just watch her try to get Efron’s girlfriend to cheat on him by seducing both her and his best bud, while Rogen gets so turned on watching it all he forgets his own role in the plan. As for Rogen himself? Here’s betting half the women in the audience find his beefy doting dad hotter than the ultracut Efron. Go figure!

There’s not much in the way of plot here, though, just Mac and Kelly’s “we’re hip” approach shifting into all-out war with the bros next door. Neighbors is more like a nonstop string of outrageous jokes—though it’s doubtful the nonbreeders out there will be ready for the movie’s unnecessarily gross lactation scene. But the extended fight sequence with Rogen and Efron using plaster-cast replicas of the frat boys’ members as weapons? The perennially immature of all ages will laugh their asses off.