Most comedy sequels are cheap cash-ins that make me break out in hives. So it was a delightful surprise that the follow-up to 2014’s so-so frat house farce “Neighbors” is a solid improvement, an enormously likable film.

They share a lightweight summer tone, adults-versus-students theme and simple story lines, but the latest version shows how carefully recycled materials can create very good products. “Neighbors 2: Sorority Rising” returns agreeable personalities to the screen, adds clever new ideas and polishes the premises it repeats.

The film opens on a happy note for Mac and Kelly Radner (Seth Rogen and Rose Byrne). Two years previous, the bonehead fraternity that operated next door drove them to distraction. They were loud after hours, made the couple feel like no-longer-hip couch potatoes and, much to Mac’s chagrin, weren’t too sharing with their weed.

Now the brotherhood has moved on, their home base is empty and a generation gap cease-fire is in effect. The Radners, preparing for their second child, are selling their house and moving up.

Across town, their frenemy from the earlier film, the eternally shirtless fitness god Teddy (Zac Efron), is finding it hard to keep a post-grad job or apartment, and dreaming about moving back into his now-deserted old home. The trio are reunited for good and ill when college newcomer Shelby (Chloe Grace Moretz) decides to turn the abandoned building into her own Partysaurus with a Greek letter title and recruits Teddy as their big brother/mentor. Which means the Radners’ house won’t sell. Let the smackdown begin, with every character a colorful piñata full of sex jokes, drug jokes, ethnic jokes and rocket-powered slapstick.

The tribal rivalry between the ages is well honed here. The film operates in five jokes a minute territory, while giving each side a solid, logical skill set. The Radners, who are seriously freaked out that their new neighbors view them as boring “old people,” are reasonably thoughtful. Even Teddy proves too senior-citizen for the new arrivals, triggering him to side protectively with the Radners, warning them that “There’s no ‘I’ in sorority.”

And while almost everything the new Greek sisters do is a dumb beginner’s mistake, they are, like, totally technologically educated. A sequence in which they sabotage the Radners’ efforts by hacking their smartphones is clever enough to make Edward Snowden burst into applause. And while there are plenty of sexist jokes here, they hit both ways and the girls are presented as people who are as funny as anyone else.

The film, which Rogen co-wrote, is a running gag about how the generation gap hits everyone. Cameos by Lisa Kudrow as the cut-you-no-slack principal and Kelsey Grammer as Shelby’s father show that no one controls hard-boiled teenagers. Rogen and Byrne’s brow-wrinkling worries about staying connected to their children show that those problems are coming on fast. Efron has some of the biggest laugh-out-loud moments by playing his dimwit character straight, giving Teddy insecurities about aging even though he’s a new Mercedes-Maybach hard body.

It’s fun to see a well-made lowbrow movie where even walk-through characters are so individual and idiosyncratic.