Paul opens in geek-paradise at the Comic-Con convention, the Mecca of nerdom. Clive (Nick Frost) and Graeme (Simon Pegg) have come all the way from England to cradle the con’s Warcraft swords and gawk at the expo’s Ewoks and scantily-clad alien women. Further asserting their nerd street cred, the British BFFs rent a Winnebago and set out to tour America’s UFO sites, including an alien-themed diner where they meet up with nerd Kryptonite: two rednecks in camouflage looking to pick a fight.

But the weirdest visitation on their fanboy frolic through the West is an actual E.T., a sassy, trash-talking green alien who’s a cross between a foul-mouthed version of the Geico lizard and another road movie hitchhiker, Jack Nicholson in Easy Rider. Paul (voiced by Seth Rogen, who summarily upstages his non-CGI co-stars) is being trailed by some nefarious government types à la Steven Spielberg’s E.T. who want to make him a specimen on their autopsy table. Their commander is an unseen, castrating woman (another sci-fi movie film insider whose distinctive voice will be instantly familiar to geek fans) who barks orders at the G-men in her employ, two nerd-like bumblers Haggard (Bill Hader) and O’Reilly (Joe Lo Truglio) and the more squared-away terminator Agent Zoil (Jason Bateman), who is determined to blast a hole through Paul.

Paul is unfortunately geared toward the lowest common denominator, coasting on an endless battery of schoolyard jokes. It doesn’t channel the wicked irreverence of adolescence; instead, it can often feel like eavesdropping on middle school playground banter. Pegg and Frost seem to believe that if you say the "F" word enough, comedy will ensue. With its endless battery of bathroom, boob, drug, and gay jokes, Paul makes Mad magazine look like The Paris Review. One or two jokes about genitalia: funny. Five or six and you’re heading into brain-dead territory. There is a spirit of teenage nastiness and crudeness to Paul that is especially unfortunate considering the air of genuine imagination and buddy comedy sweetness that infused both Hot Fuzz and Shaun of the Dead. Instead of finding something tender and nerd-cool in Clive and Graeme’s friendship, Paul offers an endless stream of jokes about how they must be gay for spending so much time together. Even the little green man piles it on, pointing out the abnormality of two grown men who enjoy nothing so much as each other’s company.

On their increasingly raucous road trip, peppered with nerd-insider references to Close Encounters of the Third Kind, Star Wars, Star Trek, and Aliens and with music from the B-52s ("Planet Claire") and E.L.O., Clive and Graeme stop in at the Pearly Gates RV park. The Pearly Gates owner is gun-toting Christian zealot Moses Buggs (John Carroll Lynch) with a lovely but sheltered daughter Ruth (Kristen Wiig). The writers use the opportunity to argue for the merits of science over religion in converting Ruth (or the "God-bothering cyclops" as Paul calls her) from a close-minded Jesus freak into a foul-mouthed, sexually curious girlfriend material. Alongside its depiction of rednecks, geeks, and clueless Hispanic room service waiters, Paul ‘s treatment of Bible-thumpers is another of the rather unimaginative, crude stereotypes that make Paul‘s comedy feel a bit mean-spirited and devoid of the good will that infuses Pegg and Frost’s other collaborations. By the time the sappy resolution rolls around, Paul feels like a guest who’s overstayed his welcome.