There is a type of recognizable character who comes from what could be called a generic southern culture. Even though the parade of personages in "Greater Tuna" live in a mythical town in Texas, they are drawn from the same southern well that seems to provide an unending source of amusement to American audiences. The two-man, 20-character show that opened last night at the Kennedy Center's Terrace Theatre attests to this appeal with refreshing irreverence.

Just why the South seems to provide so much fodder for playwrights is a question better answered by some graduate student. Cultural eccentricity, which southerners seem to specialize in, is always easier to communicate, and more fun, and certainly the authors-performers of "Greater Tuna" have spared no effort in coming up with some down-home oddballs.

This show is a hot biscuit covered with gravy; a slice of life popped out of a Texas toaster. The town of Tuna is populated by self-righteous bigots and losers, two-timing husbands and sanctimonious wives, a cliche'-spouting preacher and a wimpy humane society president, not to mention an enormous number of dogs and the incompetent radio announcers at station OKKK. The portrait may be affectionate, but it is etched with acid, and there are times when one tires of finding that each new character is even more of a feeble-brained mutant than the last.

But the show is also a tribute to the art of acting--and the art of quick costume changes. Joe Sears (the big one) and Jaston Williams (the skinny one) create new people with such extraordinary clarity that one fully expects a row of people to appear for bows at the curtain call. The wigs and clothes and false bosoms certainly help, but the quick changes would be merely gimmicks without the actors' ability to provide the sore feet of Aunt Pearl Burras, the insolent shoulders of Stanley Bumiller, or the calm voice of leadership that comes from KKK chief Elmer Watkins.

Sears has more texture than Williams, who tends to veer into an excessive broadness that makes his people seem more like caricatures than they should. Sears' Bertha Bumiller, for example, is a beehive-ed woman in lime-green polyester, complete with cellulite showing beneath her tight slacks, whose life is a continual battle--against her loutish son, her whiny and miserable daughter, the packs of stray dogs her youngest son collects, and the offensive books in the library like "Huckleberry Finn" and "Romeo and Juliet" ("it shows sex among teen-agers and disrespect for parental authority"). But she also has moments of despair in which one can see how her public morality crusades are the product of her own messed-up family.

His portraits--even the brief ones of Hank Bumiller, Sheriff Givens and the alcoholic R.R. Snavely--are more complex, allowing a sense of human frailty to balance the broad external pictures. Williams, on the other hand, reveals shades of Lily Tomlin in his portrayals, characters that are funny but for the most part lacking density.

Using the devices of the radio station and family relationships, the two actors and coauthor and director Ed Howard have structured a set of scenes that give a sense of life in Tuna. Life, that is, as seen through the eyes of these southern refugees. Anyone who has spent any time in a small town will recognize some elements, but make no mistake--the imaginations that created the town of Tuna and its inhabitants are reflecting reality through an amusement park mirror. The images may be rippled or warped or completely outsized--but they do make you laugh.

"Greater Tuna," by Jaston Williams, Joe Sears and Ed Howard, performed by Williams and Sears, directed by Howard, produced by Elliot Martin and Arnold Bernhard with Karl Allison and Bryan Bantry, scenery by Kevin Rupnik, costumes by Linda Fisher, lighting by Judy Rasmuson.

At the Terrace Theatre through Aug. 14.