"The Foreigner," Larry Shue's comedy at Olney Theatre, is like a silly party game. At first, you think you don't want to play it -- the rules seem utterly ridiculous and who, after all, wants to run the risk of having a lamp shade plopped on his head?

After about 15 minutes, however, you discover that it's kind of fun. Then you find yourself letting go. When, a couple of hours later, the host finally calls a halt to the proceedings, you realize you've had a whale of a time, carrying on, and you wear the lamp shade home in the car.

Currently prospering off-Broadway, Shue's nutty fable opened Olney's summer season Wednesday night in a snappy production that sweeps away a lot of cobwebs -- not only those that have accumulated in that Maryland playhouse over the past few years, but those that may have gathered in crevices of your own imagination. "The Foreigner" is undeniably preposterous, but it is so sweetly and ingenuously preposterous that its idiocies prove wildly refreshing.

Shue used to perform at the Harlequin Dinner Theatre in Rockville and a lot of the zaniness that characterized his performances there has made its way into his comedy. It is set in a county in rural Georgia, where the Ku Klux Klan apparently still holds some sway and the collective IQ of the populace barely breaks 100. Into this backwater, Shue introduces Charlie (Jack Gilpin), a bland Englishman for whom even idle conversation is a Herculean chore. ("I've often wondered," he wonders once again, "how does one acquire a personality?")

Charlie's wife has dismissed him as "shatteringly, profoundly boring" and cheated on him 23 times. To escape the ignominy, he has allowed himself to be whisked off to Georgia for a three-day stay in Betty Meeks' run-down fishing lodge. Only on condition, however, that he doesn't have to talk to its inhabitants. To that end, he will pose as a foreigner, incapable of understanding a word of English, although he will prove increasingly adept at spouting gibberish.

It takes Shue about half an hour to set up the various and sundry premises of his comedy. An obscure plan seems to be afoot to condemn Betty Meeks' lodge and convert it to sinister uses having to do with white sheets and blazing crosses. Likewise, there are some decided hitches in what appears to be the play's conventional romantic interest: The dashing Rev. David (Richard Bekins) has an unhealthy interest in the inheritance of his "cutie patootie" fiance', Catherine (Jacqueline Schultz). The presence of Catherine's half-wit brother, Ellard (Patrick Richwood), and a toothless redneck (John Griesemer) with a large chip on his tattooed shoulder and a switchblade in his pocket, furthers the impression that we are heading deep into "Deliverance" country.

Unlikely as it may seem, what Shue spins from these elements is a delicious red-dust fairy tale in which the dumbbells learn they are smarter than they ever suspected, the meanies are resoundingly defeated, and Charlie -- poor, nebbishy Charlie -- acquires a delightful personality in spite of himself. Forced to play the role of the exotic foreigner, he is soon improvising madly on it -- conversing in broken English, telling tales in his imaginary native tongue and inventing such nonsensical customs as the wearing of the juice glass (inverted on the top of his head) after breakfast. As he brings the downtrodden rustics out of their shells, he discovers, miraculously, that he has shed his own. Don't let anyone spoil the climax for you, which has the KKK storming this sorry outpost. Suffice it to say that Shue borrows a page from "The Wizard of Oz" and it's a show-stopper.

For the most part, Olney's production has been immaculately cast and directed by Charley Lang, who never lets Shue's silliness outrun itself. By holding back in the early stretches and making sure the foundation is solidly in place, Lang reaps a rich harvest of laughs later on. I dare say you will even come to look upon come these bumblers and rubes as more than simple caricatures. Overall, there's a lovely innocence to the play, and this production honors it. The fun may be rooted in the characters' limited intellects, but it is never demeaning.

In fact, quite the funniest, fullest and sweetest character is the stupidest. For Ellard, the ignorant brother, a question like "How do you like your eggs?" is a true conundrum. But if this benighted creature is bereft of brain power, Richwood, who looks a little like a lost question mark, gives him a boundless heart, insatiable curiosity and the enthusiasm of a marching band. Instructing the foreigner in the rudiments of backwoods English -- "faw-werk" for "fork," "lay-ump" for "lamp" -- Ellard progresses from half-wit to, say, three-quarters-wit. Richwood makes the transformation hilariously inspiring.

At the same time, the foreigner is undergoing his transformation -- from scared titmouse to king of the jungle. Gilpin orchestrates it masterfully, forging gleefully ahead even as his innate timidity holds him back. Fine, too, are Schultz's blond debutante, Griesemer's slimy villain and Vivienne Shub as the gabby old cuss who runs the fishing lodge and claims an intuitive understanding of all foreign languages, real or otherwise.

Granted, Bekins is a bit stiff in this company, as the duplicitous reverend, and Tony Rizzoli, as a British army consultant, can't quite counter the impression that his character serves mainly expository purposes. But they are minor drawbacks in an evening of gathering merriment. "Blasny, blasny," says the foreigner, who by the end has taken to his new surroundings like a cat to a creamery. That, of course, translates as "Ain't dees nice!" And it applies equally to this offbeat comedy, which gets Olney off to its strongest start in years.