GRANDMA'S BOY — * 1/2 — Allen Covert, Peter Dante, Shirley Jones; rated R (drugs, vulgarity, profanity, violence, nudity, sex); Carmike 12 and Ritz 15 Theaters; Century Theatres 16 (Salt Lake City); Cinemark 24 at Jordan Landing; Megaplex 17 at Jordan Commons.

If you're a video game geek and/or a stoner, "Grandma's Boy" isn't a comedy — it's a documentary.

For everyone else, it's an interminably flat, one-joke movie with admittedly a couple of decent laughs. (Not surprising, it wasn't screened for critics before opening day. January is dumping-ground time, after all.)

Longtime Adam Sandler pal Allen Covert leads this unabashed celebration of arrested development as Alex, a 35-year-old video game tester who's forced to move in with his grandmother (Doris Roberts) and the two friends (Shirley Jones and Shirley Knight) with whom she shares a primly decorated Victorian.

You know it's only a matter of time until these golden girls mistake his stash for tea and end up rolling on the floor in uncontrollable giggles — though the running joke about Jones' character's sexual history with half of Hollywood is sort of a hoot, and it's oddly riveting to see her get her freak on here with a guy who's about 50 years her junior.

Linda Cardellini (Velma from the "Scooby-Doo" movies) co-stars as an inordinately attractive video game expert, and several of Sandler's fellow "Saturday Night Live" alums make their usual appearances, this being A Happy Madison Production and all.

The movie does have a loopy spirit of multicultural, intergenerational bonding that's almost endearing, though. Alex's co-workers are twentysomething nerds of various ethnic backgrounds, and his drug dealer, Dante (Peter Dante), has a never-ending stream of diverse visitors who laze on the couch and sample his product.

Naturally, they all end up at the kind of raging party that only takes place in the movies, where bikers and grandmothers forge unexpected friendships over beer and breakfast cereal (everyone gets the munchies, regardless of age).

But that's the entirety of the film, directed by Nicholaus Goossen and written by Covert, co-star Nick Swardson and Barry Wernick. They smoke pot, they play video games, they goof on each other. Each character has his or her own joke that they're saddled with the whole time. One particular misfit (Joel David Moore), the company's scrawny child prodigy, thinks he's Neo from "The Matrix" and talks to himself in a nasal robot voice when he's nervous, a shtick that grows annoying quickly.

The most intriguing aspect of sitting through "Grandma's Boy" is watching Covert and marveling at how much he looks and sounds like Mel Gibson. It makes you wonder what he and the rest of the Happy Madison crew could do with "The Passion of the Christ."

"Grandma's Boy" is rated R for drug use, strong language, strong crude and sexual humor, and nudity. Running time: 95 minutes.