With no big, glossy Meryl Streep comedy or Kathryn Stockett adaptation coming out this year, August was looking like a pretty charmless month at the movies. Oh sure there are some smart and winning indies out there, but who has the energy to seek those out? All most of us want to do is drag ourselves to the nearest megaplex, flop into a seat, and be entertained for a few hours while we wait, wistful but ready, for fall to arrive. So, it's lucky for us that along comes We're the Millers, a slight and silly comedy that nevertheless provides a welcome dose of light frivolity in this otherwise dark, turgid, non-blockbuster summer.

Mind you, this isn't Woody Allen. It's not even Judd Apatow. Instead it's one of the comedies that feels like a semi-distant descendant of the earlier Apatow films — it might be The 40-Year-Old Virgin's cheaper, more free-wheelin' great nephew. A comedy about a group of disparate losers — a low-level pot dealer, a tired stripper, a bitchy street kid, and a neglected boy virgin (I guess that's a bad enough lot in life for an 18-year-old boy) — pretending to be a family so they can smuggle a couple tons of weed across the U.S./Mexico border in an RV, We're the Millers is a crass caper comedy that manages to infuse the madcap, profanity-laden antics with an easy, laid-back strain of humanity. Credit for that should of course partly go to the four credited screenwriters and director Rawson Marshall Thurber (Dodgeball), but really we've the game and playful cast to mostly thank for the movie's bouncy but low-key improvisatory rhythms.

In his first true starring role, Saturday Night Live vet Jason Sudeikis acquits himself well as our shaggy, ne'er-do-well (anti-)hero, David. He's a sour, hangdog jerk, but we know there's a good heart underneath all that grime. Sudeikis doesn't overplay that innate sweetness, which will of course burble up to the surface by picture's end, keeping a good grasp on David's sharpness and self-interest without making him irredeemably unlikable. Jennifer Aniston, the winsome comedienne of exactly one graceful note, plays Rose the stripper, tired-eyed and edgy, a ribbon of elusive and largely unspoken sadness running through her, as is true of all of Aniston's characters.

Their children, for the purposes of this mission anyway, are Kenny and Casey, played by a goofy and endearing relative newcomer named Will Poulter and the perpetually employed but only ever loosely defined Emma Roberts. Roberts has yet to prove her true bona fides as an actor, but here at least doesn't intrude on or slow the movie's flow; in fact in certain scenes she taps right into it, most notably in one squirmy sequence that has Kenny kissing his fake mom and fake sister as they teach him how to snog a girl. Poulter, who seems a bit more suave in real life, plays this scene and all others with noodly panache; Kenny is the geeky heart of the film, but is never condescended to or treated as anything more extreme than a soulfully quirky kid. For a movie with a premise as absurd as We're the Millers's, the quartet at its center somehow feels like a bunch of real people.

Nearly walking off with the movie in a few key scenes, Kathryn Hahn turns in yet another vital supporting performance as a buttoned-up fellow RVer with some darker passions roiling under her sensible slacks. (Though I do wish, in once scene, she'd used another euphemism instead of "hotdog down a hallway." That's beyond tired. We need something new. Tugboat in a cruiseport? Something, please.) Parks and Recreation's Nick Offerman plays her husband, doing a riff on his Ron Swanson character from Parks, replacing Ron's sturdy if antiquated manliness with a squishier Midwestern plainness.

The conceit of We're the Millers is, of course, that while pretending to be a family, these raggedy folks actually do become one. And while the script does wander into the shallows of treacle on occasion, especially in Sudeikis's big, inevitable "I love these people" monologue toward the end, those few missteps are made up for with smaller and even wiser moments, subtler shifts in mood and feeling. Casey lets a quick, happy smile dart across her face after being scolded by her fake parents. Kenny and David share an awkward father/son moment. David and Rose begin to tingle with prickly, sexy chemistry while playing house. Though mostly a raunchy road comedy — complete with a few quick shots of Kenny's tarantula-bitten scrotum — We're the Millers knows when to huddle in closer and speak more quietly, even honestly. The film is mostly a late-summer trifle, a junk drawer full of clever gags, but amid all the misguided seriousness that's plagued movie houses this summer, a bit of breezy, bawdy bonhomie feels as refreshing as a dip in the pool.