“We’re the Millers” is an identity comedy with identity issues.

Jason Sudeikis plays a pot dealer who, as a disguise for smuggling a huge shipment of weed, forms a fake family to drive an RV across the Mexico border. He gathers local stripper Rose (Jennifer Aniston), surly homeless teenager Casey (Emma Roberts) and his young, naive neighbor Kenny (Will Poulter).

The whole concept has two motives: to lampoon the idea of the traditional all-American family, and as an excuse to get Aniston to take off her clothes. Both are worthy endeavors, but everything in “We’re the Millers” feels forced.

Despite obvious comedic talents, Sudeikis and Aniston have each had difficulty finding their place in the movies, and neither really fit their parts: small-time Denver pot dealer (dispatched for the pick-up by Ed Helms’ polite but ruthless drug lord) and bitter stripper with a heart of gold, respectively.

The concealed identity shtick would have been more fruitful if the characters’ personalities weren’t just as thin as their charade.

The script was begun by “Wedding Crashers” scribes Bob Fisher and Steve Faber, and finished by “Hot Tub Time Machine” writers Sean Anders and John Morris. “Dodgeball: A True Underdog Story” director Rawson Marshall Thurber keeps the tone appropriately breezy, but understandably struggles to find the right sense of timing.

“We’re the Millers” aims for a nuclear family farce, pushing it one step further than its obvious inspiration, “National Lampoon’s Summer Vacation”: Not only are they not the gleaming picture of family life they might seem, they’re not even a real family.

Every pit stop is a chance for gratuity. There’s a camp out with swingers (Nick Offerman and Kathryn Hahn) and a run-in with pursuing drug dealers that inanely becomes Aniston’s strip tease. As she did in “Horrible Bosses” (which also co-starred Sudeikis) the actress trades on the thrill of her sexuality, which wouldn’t be necessary if a good romantic comedy script captured her girl-next-door snark. But it’s starting to look unlikely she’ll ever find another “The Good Girl” — or is really seeking it.

As a diversion, one could do worse. Sudeikis’s smart-alleck, Midwest charm, masking a more devious instinct, does a lot to carry the film. The former “Saturday Night Live” player has struggled to transition to leading man roles, though he showed promise in the little seen “A Good Old Fashioned Orgy.”

But he’s straining here to keep the ship righted. When the end-credit bloopers roll, Sudeikis and Aniston, free of the contrived plot, look like they’re finally having fun.