Alien encounters are one of the many sci-fi genre traditions lampooned in "Paul."

“Paul,” the new science-fiction comedy adventure film directed by Greg Mottola, has all the trappings of great entertainment. The movie’s cast—its two notoriously funny leading men, Simon Pegg and Nick Frost, as well as its superb secondary crew featuring the likes of Jason Bateman and Seth Rogen—has great promise. Combine such a comedic class act with a host of satirized sci-fi tropes, from Area 51 to the government agents who dependably hunt down alien visitors to our planet, and you have the makings of a great film. However, for all its potential, “Paul” often feels as hackneyed as the science-fiction movies it claims to parody. Fortunately, though the film fails in its attempt to push the envelope, the all-star actors of “Paul” provide plenty of laughs.

The premise of “Paul” is a familiar one: two strapping young men looking for adventure head cross-country on a road trip in the greatest of American vehicles, an RV. “Strapping young men,” however, is not an entirely apt description of Graeme Willy (Simon Pegg) and Clive Gollings (Nick Frost). More accurately, they are two paunchy man-children with British accents who dream of making it big in the comic book world. Their road trip is quickly  interrupted by the arrival of Paul (voiced by Seth Rogen), an alien who requests their help. The group soon sets out to return Paul to his mothership—with the military in hot pursuit.

This CGI character of Paul, brilliantly brought to life by Rogen, is the highlight of the film. In fact, the source of most of the humor in “Paul” is not the ability of Frost and Pegg—who are also the film’s writers—to satirize prior films, but rather their ability to imbue Paul with all the reasonableness and sensibility that Graeme and Willy so sorely lack. For example, when Graeme asks Paul if he is about to probe them, Paul retorts, “why does everyone always assume that? What am I doing? Am I harvesting farts? How much can I learn from an ass?”

Paul’s backstory is as cleverly constructed as his dialogue—in one scene, he is shown advising Steven Spielberg—and provides originality in an otherwise undistinguished script. While Pegg and Frost perform well in their familiar roles, Rogen’s alien, by contrast, is stereotypical only in appearance, otherwise exhibiting an unusual penchant for beer, weed, and pop culture references. All in all, Paul possesses the comedic creativity that many of the film’s running gags and various attempts at genre parody do not.

“Paul” is peppered with pleasant surprises from its other supporting actors, including Jason Bateman as a deadly serious government agent, Jeffrey Tambor as a jaded comic book author, and a criminally underutilized Jane Lynch as a waitress at a space-themed diner. Graeme’s love-interest, Ruth, is played with relish by comedian Kristin Wiig, even though the actual role seems to have been written with half the inspiration of her performance. Wiig makes the best of her meager material, namely, a running gag that has her cursing in nearly every line when Ruth—a lapsed resident of the Bible belt—decides to sin with reckless abandon.

All things considered, “Paul” provides mild laughs, with a few side-splitting exceptions, for a decidedly mainstream audience. The film’s commercialized appeal makes for a starkly unfavorable contrast between “Paul” and Frost’s and Pegg’s exponentially funnier collaborations with director Edgar Wright, “Shaun of the Dead” and “Hot Fuzz.”  While those movies pushed audiences’ limits and had resultant moments of comic genius, “Paul” takes a safer—if more lucrative—route, settling for taking easy shots at Bible-thumpers and comic-book nerds.