Making a high-concept, special-effects comedy must seem like a great idea. Just find a bunch of funny guys and throw some ghosts or aliens at them. Between the explosions, the jokes and the green slime, there’s something for everybody. The obvious example here is Ghostbusters. But making a successful special-effects comedy — balancing the tone throughout, making sure the jokes are funny and the story is actually interesting — is evidently a lot harder than it looks. Even Ghostbusters director Ivan Reitman couldn’t replicate it, as anyone who has seen his film Evolution can attest. The Watch is fairly funny, but the alien invasion part of the story is never as engaging as the scenes in which the characters are just messing around.

Ben Stiller plays Evan Trautwig, an uptight suburbanite who is the general manager of the Costco in Glenview, Ohio, which, according to him is the happiest place on Earth. This isn’t so true anymore after the night watchman at Evan’s store is brutally murdered. After the local police prove themselves to be woefully inept at catching the killer, Evan forms a neighborhood watch to solve the crime.

Several weird new friends join Evan in the watch. Vince Vaughn plays Bob, an overeager guy who wants to have a close relationship with his teenage daughter, but the best he can manage is stalking her on Facebook. Bob sees the watch as a way to make some new male friends, and if he has to fight crime to do it, then so be it.

Jonah Hill plays Franklin, a super-intense twentysomething who was rejected by the police force and sees the neighborhood watch as the next best opportunity to kick a little ass.

Rounding out the group is Richard Ayoade, a British actor and director probably best known to American audiences from the sitcom The IT Crowd, playing Jamarcus, a recent divorced man who has dreams of lonely housewives coming up with creative ways to express their gratitude to the neighborhood watch.

Vaughn’s role is ideally suited for him, allowing him to run with his wide-eyed, motor-mouth schtick. It’s a familiar role for Vaughn, but he’s very funny here. Stiller also plays a familiar role here. Having the dubious virtue of being the lead, he again finds himself essentially playing the uptight straight man. Hill is playing something we haven’t seen him do before, but his character is very reminiscent of Seth Rogen’s character in Observe and Report or Nick Frost’s character in Spaced.

The most unexpected dynamic in the group comes from Ayoade, who always seems on a slightly different wavelength from the rest of the group. Many of the film’s biggest laughs come from him, and his brand of comedy is a welcome change from the rest of the actors.

The guys are all so starved for male bonding that they spend most of their time hanging out and drinking beer, making only cursory attempts to fight any crime. These early scenes are loose and hilarious, and probably the best in the movie, as Vaughn, Hill and company seemingly improvise their way through scenes.

Eventually, though, the film’s science-fiction plot kicks in, when the guys discover that aliens are responsible for the murder, and are planning a full-scale invasion of Earth. For some reason, instead of calling the FBI or CIA or Men in Black, the characters decide to fight the aliens with the guns Franklin has stashed under his bed. Despite the efforts of director Akiva Schaffer (Hot Rod), the movie never seems very interested in the particulars of the alien plot, and it’s hard for us to care too much, either. The laughs don’t stop completely, but they do slow down amid all the running and shooting and explosions, and the movie suffers for it.

The script is credited to Seth Rogen and Evan Goldberg, along with Jared Stern. These disparate writing credits (Rogen and Goldberg wrote Superbad and The Pineapple Express, while Stern wrote The Princess and the Frog and Bolt) likely speak to the long and winding road the movie took through studio development. The finished product looks mostly like Rogen and Goldberg’s work, in both good and bad ways (it’s gleefully foul-mouthed, but it also includes some incongruously gross gore), but it seems a little too impersonal to really feel like there’s much of a singular, driving artistic voice behind the movie.

If there is any driving force behind the movie all, it’s probably Costco. The store and the brands within it are so lovingly photographed that it starts to feel a little icky, as the movie approaches satire of product placement and then charges straight on into whoredom. (And I wonder how the makers of Rayovac batteries will feel about how their product is used in the film.)

There was a British movie last year called Attack the Block that executed a similar premise much more successfully. If this movie had been more like that one, or had just been about a bunch of guys goofing off while pretending to fight crime, then I think it would have been more successful. As it stands, The Watch is pleasant enough for a while, and never outright bad, but the charms of its leads aren’t enough to sustain interest once the alien plot kicks in.