Rated R

Ever have a hankering for a nice ham sandwich, only to discover you have nothing but plain white bread, one aging slice of ham, and no mustard in the fridge? “Paul” is kind of like that. In this model, the white bread is represented by celebrated British wonder-nerds Simon Pegg and Nick Frost, and the ham by all-American stoner Seth Rogan. The absence of mustard is sadly portrayed by a lack of wit and inspiration.

It’s a disappointing slip for the writing/acting pair of Pegg and Frost, whose previous collaborations have produced the now legendary zom-com “Shaun of the Dead” and the remarkably astute buddy-action send-up “Hot Fuzz”—two films that managed to repackage the tired conventions of their respective genres into interesting and original stories that served as sharp observations of their sources and rippingly funny character pieces. 

Their latest foray into fromage homage territory leads into a similarly familiar land of childhood movie favorites, this time assimilating an odd combination of adventurous road trips like “Smokey and the Bandit” and “The Blues Brothers” and extraterrestrial first contact films like Steven Spielberg’s “Close Encounters of the Third Kind” and “E.T.” 

In “Paul,” Pegg and Frost play a pair of socially inept, slightly codependent, Comic Con boy-men (just a lower-functioning, disadvantaged projection of their actual selves, really) who encounter a bona-fide little green dude from outer space who’s on the run from captivity and certain death at Area 51.

Their journey across the U.S. Southwest to deliver him from the pursuing government Men In Black to a rendezvous with an alien rescue ship brings them in contact with a long string of American stereotypes—drunken rednecks, Christian fundamentalists, gum-chawing waitresses and gun-toting cops—all of whom serve as blunt reminders that our pair of twee English blokes 1) are the true aliens of the story, and 2) don’t think very highly of Americans. 

Even the little visitor Paul (so named for the dog his spacecraft squished upon the impact of his disastrous arrival on Earth in 1951), as voiced by Rogan, is alien in form only. He smokes blunts and moons people, munches hot wings and swills cheap brewskies by the campfire. It seems decidedly improbable that even a universe of infinite possibility would produce extraterrestrial life forms that mimic No-Cal slackers with such precision. It’s a joke that may have worked on a much smaller scale. But the film’s gags rely too heavily on torrents of puerile profanity (the only apparent reason for its “R” rating) and cheap, redundant pratfalls (did we really need three fainting scenes?), and the conceit wears exasperatingly thin as the show rolls on.

The proceedings are amiable enough, and Pegg/Frost’s clearly heartfelt affection for their inspirations helps to anchor the helium-light plot. But they wield their obviously keen and practiced insights more like a club than a laser. Instead of exploring the themes, characters or—dare it be said—cultural subtexts that made those classic movies so endearing and enduring, they choose simply to quote from them directly—in music, locations, cinematography, even lighting design, and especially in dialogue. Surely, the geeks of the world (who will undoubtedly be thrilled to chase down all the sci-fi Easter eggs planted throughout) will bat movie lines back and forth between each other as if it were real conversation, but there’s just something disingenuous and artificial about having the Han Soloisms and catch phrases from “Jaws” and “Aliens” and “Back to the Future” start spilling from the mouths of the “norms” onscreen, too. 

The constant, almost slavish references to the works of Spielberg, Lucas, Cameron, Zemeckis and Jackson become an increasing distraction, and it grows uncomfortably apparent in the final reel that our good guides have finally just left the pavement. Though some weak gestures are made to the kind of honest character work they became famous for, the characters in “Paul” are so transparently contrived from known material that it’s impossible to develop any real interest in them.

In the past, Pegg and Frost have enjoyed the benefit of working with visionary director Edgar Wright, and the success of their prior efforts may very well be due to his particular instincts for translating their singularly complex kind of humor. But “Paul” director Greg Mottola, whose “Superbad” shared a similar brand of filth, bromance and outsider self-actualization, doesn’t appear to have the Wright stuff. 

Lacking Wright’s signature visual flourish may be no fault of his own, but one can’t help but think that such broad material could have been made far more digestible in less literal hands. 

Paul is by no means a horrible film, but there’s every reason to expect great things from these guys, and it just isn’t that great. There are plenty of fanboys out there who will still say Pegg and Frost can do no wrong. Well, sorry to tell you, they sure can do a lot better.