A family packs into a truck or RV and hits the road for a trip across the country. Shenanigans ensue, splitting the clan up and then eventually bringing them back together with a couple of new life lessons for the crowd-pleasing finale.

In "We’re the Millers," however, there is one major deviation: The family isn’t a family. They’re just a bunch of down-on-their-luck lowlifes, shoved together and dressed up in their white bread Norman Rockwell-iest. And while there are few surprises in the screenplay, the surprises come in how many laughs this contrived little twist – and the game cast – manages to pick up along its well-tread path.

Jason Sudeikis stars as the fake family’s drug dealing patriarch David Clark. After getting his stash robbed by some street punks, David must repay his smarmy drug kingpin boss – and former college pal – Brad (Ed Helms). Brad’s idea is simple: David upgrades from dealer to smuggler, heads down to Mexico and picks up "a smidge and a half" of pot. It’s simple because David has no choice but to accept it.

On his own, David figures he’ll be an obvious target for a search and destined for an unpleasant stint in a Mexican prison. He’s ready to accept his incarcerated fate when he sees an overly chummy family (a "real life Flanders" as he calls them) pull up next door in an RV and charm a grumpy cop out of writing a ticket. Cue the light bulb: He’ll hire some people to pose as his family, and border patrol won’t bat an eye.

With the help of a little money, David assembles his perfect fake family, complete with his dweeby teenaged neighbor (Will Poulter), an angsty homeless runaway (Emma Roberts) and playing the role of wife, the money-desperate stripper next door with a heart of gold (Jennifer Aniston).

He throws pastel-colored polos on everyone, and they hit the road together to snag his boss’s precious herb thanks to the power of white privilege, something that’s a part of the joke … if just barely. How else do you explain a scene in which border patrol abandons the Miller RV, literally oozing marijuana out of every pore, to viciously hunt down a barely seen posse of illegals. Lazy screenwriting that wrote itself into a hole and was in desperate need of an excuse to get the family back on the road? I’ll give them the benefit of the doubt.

I have a harder time giving the rest of the script – coming from a team of four writers ­­– a pass. It starts off rough with a montage of classic YouTube videos for some cheap laughs (audiences didn’t pay $10 to see something they could watch at home in their underwear) and gets a little bit better as it goes along, mainly because it can only go up from there.

Brad’s smidge and a half of pot ends up being about a hundred bags more than a smidge … and also not his pot. The stash actually belongs to a dangerous Mexican kingpin (Tomer Sisley). When the clan isn’t running from him and his one-eyed mountain of a henchman, they’re trying to escape a cheery band of fellow travelers (Nick Offerman and Kathryn Hahn) with DEA connections.

Each of these little plotlines comes with their own set of predictable raunchy hijinks and contrived close calls, including a bag of weed disguised as a baby named LeBron. Perhaps the RV is giving off fumes too, because Offerman and Hahn’s cheerful tagalongs buy it.

"We’re the Millers" is deeply committed to following the road trip formula. If the film was a driver, it’d have its eyes firmly glued to its Garmin, attentively listening to the creepy robotic voice’s directions. In five miles, take a right turn at the third act fight that divides our characters just when it seemed like they were finally bonding. Recalculating. Take a U-turn; the main character realized his error of his selfish ways. Arrive at heartwarming destination.   

But it’s amazing how much forgiveness an unassuming, by-the-books comedy like "We’re the Millers" can generate with some solid laughs and an enjoyable cast.

I used to dislike Sudeikis (there was something annoyingly smug about his delivery that bothered me), but he’s managed to win me over. Here, he’s basically doing a take on Vince Vaughn’s patented everyday mope fast-talking his way in and out of trouble but with the casual charm and freshness Vaughn’s lost due to repetition. He makes the most out of the material, especially when he’s mockingly chatting with a gangly redneck wannabe gangster who ends every sentence with "yaknowwutimsayin?"

Playing the role of scene stealer is Poulter as the clan’s dopey but big-hearted teenaged son Kenny. The Brit plays it just right, going sincere and sweet instead of overplaying the character’s dorkiness. The movie also gets a lot of bonus help from the various comedy veterans (Offerman and Hahn, Thomas Lennon, Ken Marino) that come and go, leaving their hilarious marks. The only dull member is Aniston, who’s basically just around to strip and play romantic interest.

Director Rawson Marshall Thurber, who mastered the art of throwing stuff at dudes with 2004’s "Dodgeball" and those terrific Terry Tate: Office Linebacker ads, isn’t much for style or sophistication, but he keeps the jokes coming and the pace brisk. The movie almost clocks in at two hours – borderline sinful for a comedy – but Thurber keeps the film on its feet and therefore alive.

Near the middle of the film, fake son learns how to kiss thanks to his fake sister and fake mother. They pass him back and forth, locking lips and teaching tricks, all the while dad noshes on chips and takes photos on his phone. The audience knows it’s only a matter of time before the cute girl Kenny has the hots for walks in. Lo and behold, a few kisses later, the crowd’s power of precognition was proven right.

That perverse highlight is pretty much "We’re the Millers" in a nutshell. It’s easy to see exactly where it’s going at all times, but there are enough laughs along the way to keep me from turning this car around.