In the aftermath of the Trayvon Martin shooting in Florida, the studio altered the title of this brainless comedy from “Neighborhood Watch” to the current stripped-down version. They should have kept the name and changed everything else instead.

The picture is essentially an “adult” version of the kids’ flick “Aliens in the Attic,” which the same studio released a few years ago. In that movie, a passel of youngsters, ranging from teens to tykes, successfully fought off a bunch of rubbery extraterrestrials that had invaded their family’s vacation home with plans to conquer earth. In “The Watch” a bunch of goofball neighborhood watch volunteers do battle with an outer-space army that’s infiltrated their town. But in comparing the two pictures, it would be unfair to equate the bumbling suburbanites with the kids of the earlier film. The youngsters in “Attic” were far more likable and intelligent than the idiots that populate this movie—most belonging to that species of infantile guys that, following in the footsteps of Adam Sandler and Will Ferrell, seems to be the only sort of male Hollywood is capable of portraying in comedies nowadays.

Of course, being written by the team of Seth Rogen and Evan Goldberg (along with Jared Stern) and aimed at the audience that laps up Judd Apatow’s product, it’s unlike “Attic” in being done on a much larger canvas—the town of Glenview, Ohio rather than a single house—and being unremittingly crude and nastily violent to boot. The dialogue consists of little more than a barrage of coarse sexually-based lines (they’re too flat and tedious to be called banter), and the action, when it doesn’t go the route of oddly unpleasant fights, shootings, blood-and-goop-letting and explosions, opts for even more repulsive potty humor and gags about date-rape and orgies. The idea is to get laughs from sheer tastelessness, but in this case, with a few rare exceptions, the tastelessness remains nothing more than that.

Ben Stiller plays his customary nebbish character—Evan, the straitlaced manager of the local Costco store (the chain is shamelessly plugged throughout, down to the use of its advertising catchphrase). A dolt known for founding clubs, Evan is aghast when his night watchman Antonio (Joe Nunez), a chubby jerk who spends his on-the-clock time guzzling booze and drugs while watching TV, is brutally killed (and, we’re told, skinned) during his shift. Evan immediately forms a neighborhood watch to catch the killer and save his perfect burg, but the only guys who join are Bob (Vince Vaughan), a motormouth doofus who sees the group as a means to get some drinking buddies, Franklin (Jonah Hill), a police-department reject and would-be vigilante with a chip on his shoulder and a secret arms cache under his bed, and Jamarcus (Richard Ayoade), a weird, frizzy-haired fellow with an odd demeanor.

To make a long story short, the killers turn out to be a bunch of large lizard-like aliens that are murdering people to hide in their skin, “Invasion of the Body Snatchers” style (though, in fact, remarkably little is made of this tidbit of information) while using Evan’s store to build the transmitter with which they’ll summon their invading armada to take over the planet. That will, of course, lead to a big final confrontation at Costco between the guys and the nasty outer-space villains.

But along the way to that finish, the script throws in some strangely tone-deaf sidebars. There are a couple of other deaths, of a punk kid (Johnny Pemberton) and an irascible ex-Marine (R. Lee Ermey), in scenes that try for some genuine suspense but, as directed uncertainly by Akiva Schaffer, haven’t the heart to pull it off. (Nothing much comes of them, either—the most obvious of the script’s dangling plot threads.) There’s a gruesomely unfunny subplot about Paul (Billy Crudup, uncredited), a peculiar new neighbor that Evan suspects of being a pod-person but who has something else going on, and another about a smarmy cop (Will Forte) who disses the watch guys incessantly. And there are the elements intended, feebly as it turns out, to add a bit of sentiment to the mix—a secret Evan’s keeping from his wife Rosemarie DeWitt) and Bob’s concern about his daughter’s (Erin Moriarity) taking up with a surly classmate (Nicholas Braun).

All together, these various elements provide little for the cast to work with. Stiller and Vaughn both do their increasingly tired shtick, while Hill looks almost as clean-cut as he did in “Moneyball” but is stuck with a role that’s rather creepily reminiscent of some people’s worst suspicions about George Zimmerman. The most interesting performance, in fact, comes from Ayoade, who offers what’s pretty much a caricature but is at least one we haven’t seen before. (A twist involving Jamarcus is yet another item that recalls “Aliens in the Attic.”) DeWitt is wasted in a thankless role, Ermey simply shouts obscenities, and Forte adds to his string of pallid sketch-comedy-quality feature bits. The technical credits are okay across the board, with monster effects that are really better than the material deserves.

But “The Watch” isn’t worth watching, despite a few moments—like a reference to Nickelodeon’s kids’ awards—that might earn a smile. If you want to see a movie along these lines that’s actually somewhat better and don’t want to go the kiddie “Aliens in the Attic” route, you might try Joe Dante’s “The ’burbs” (1989). It’s not one of that director’s better pictures, but it’s certainly preferable to this.