In the cheerfully pious voice-over that begins “The Watch,” a ramshackle science-fiction comedy desperate for laughs, the movie’s narrator, Evan (Ben Stiller), proclaims his hometown, Glenview, Ohio, the most wonderful place in the universe. He insists that he is not in the least interested in what might be “out there,” or in living anywhere else.

Evan has second thoughts upon discovering a hive of lobster-y extraterrestrials nesting in the basement of the Costco that he manages. The invaders’ first strike against humanity is the murder of the store’s security guard. As the movie shuffles aimlessly along, Evan’s baby blues widen with fright and fascination like those of Henry Thomas, as Elliott, in “E.T.: The Extraterrestrial.”

The aliens, armed with laser guns, are tricky little devils who don’t reveal themselves completely until late in the movie. In a whimsical nod to “E.T.,” Evan’s initial contact, in which a creature gracefully accepts a piece of gum, seems benign.

Joking references to an ’80s blockbuster don’t mean that“The Watch” is a throwback. With its endless phallic jokes — references to Magnum condoms, green alien blood with the texture of semen, panic about infertility (Evan is afraid to tell his wife that he is “shooting blanks”) and well-endowed invaders with brains in their genitals — “The Watch” is the latest in a wave of comedies drenched in male sexual anxiety.

Directed by Akiva Schaffer from a screenplay by Jared Stern, Seth Rogen and Evan Goldberg, the movie clumsily juggles two loosely connected concepts. In the spirit of “The Hangover,” it is a whimsical, potty-mouthed buddy movie that lunges for laughs with bursts of profanity; it is also a spoof of “Invasion of the Body Snatchers,” in which the aliens disguise themselves as humans.

Paranoia radiates outward from the groin in every direction. In one scene Evan and fellow members of the neighborhood watch group he leads are so consumed with suspicion while in a supermarket that images of a child licking an ice cream cone or of a woman inspecting a grapefruit are fraught with terror. Unwittingly or not, the movie satirizes the national obsession with security with lethal accuracy.

Evan, who founded the watch group, is one of its two members who are unequivocal wimps. A friendless control freak who fancies himself a model citizen, he is so afraid of incurring the wrath of his wife, Abby (Rosemarie DeWitt, in a barely sketched role), that he is reluctant to sleep with her. The other wimp is Franklin (Jonah Hill), a creepy gun nut who still lives with his mother and is still smarting from being rejected by the police. But underneath his ridiculous macho preening is a quivering marshmallow.

They are joined by Bob (Vince Vaughn), a boisterous, beer-loving jock who is pathologically obsessed with the purity of his teenage daughter, and Jamarcus (the British comedian Richard Ayoade, ill used and unfunny), an eccentric wild card with a fetish for Asian women. They form the most timid and incompetent quasi-vigilante group you could hope to encounter in a small town.

The movie builds to a human-versus-alien showdown so sloppily staged that it makes little visual sense. The bargain-basement pyrotechnics suggest that much of “The Watch” was filmed on autopilot on a strict budget.

“The Watch” is rated R (Under 17 requires accompanying parent or adult guardian). It has strong language, profanity and violence.

The Watch

Opens on Friday nationwide.

Directed by Akiva Schaffer; written by Jared Stern, Seth Rogen and Evan Goldberg; director of photography, Barry Peterson; edited by Dean Zimmerman; music by Christophe Beck; production design by Doug Meerdink; costumes by Wendy Chuck; produced by Shawn Levy; released by 20th Century Fox. Running time: 1 hour 38 minutes.

WITH: Ben Stiller (Evan), Vince Vaughn (Bob), Jonah Hill (Franklin), Richard Ayoade (Jamarcus) and Rosemarie DeWitt (Abby).