In a season overstuffed with sugarplums, it's nice to encounter a sourball. The comedy "A Tuna Christmas," back for a second year at the Kennedy Center's Terrace Theater, takes a raucous, irreverent attitude toward the sacred season; it's the show for everyone who understands what P.G. Wodehouse meant when he wrote, "Christmas is almost at our throats again." But like a good sourball, "A Tuna Christmas" has a sweet center. By celebrating the worst of Christmas so zestfully, the play earns the right to its poignant, shyly happy ending.

"A Tuna Christmas" is a sequel to an earlier show with the same author-actors, Joe Sears and Jaston Williams. Here, as in the original, they not only (in collaboration with the director, Ed Howard) wrote the material, they also play all the roles. This amounts to 12 characters each, female and male, young and old, crazy and not- quite-as-crazy. Surrounded by endless, empty prairie, Tuna, the third smallest town in Texas, is hard on its natives. They tend to become quietly sad or flamboyantly bonkers, and they lighten their dull lives by making trouble for one another. The Christmas season brings to hilarious fullness their envy, ambition and creative malice.

The play doesn't exactly have a plot. The excuse for the shenanigans that take place is the annual Tuna Christmas Yard Display Contest, which the rich and unpleasant Vera Carp has won for 14 straight years. Will she win again? All the other story elements hang from this central question like ornaments: the Tuna Little Theatre's production of "A Christmas Carol" (the director, a pretentious outsider who last season put on the Tuna premiere of "No Exit," has cut Tiny Tim); Stanley Bumiller's hopes of finishing his community service and ending his probation; Bertha Bumiller's lonely efforts to hold her fractious family together; the Smut Snatchers' attempts to clean up Christmas carols ("round yon virgin" has to go).

Two actors creating a whole community is something of a theatrical stunt. It's to Sears and Williams' credit that they often bring real emotion into what could be just a series of funny turns. They are helped enormously in their task by Linda Fisher's terrific costumes. Getting into Fisher's chenille bathrobe or donning a hat she has designed that reads "Save the Fire Ants," the actors literally put on their characters.

Williams is more of a caricaturist than Sears. His women in particular, with their amazing shoes (transparent plastic high heels; pink stiletto slippers with feathery toe balls) are loony expressionist sketches. Occasionally he overdoes it. His shrewish Didi Snavely, who screams at her husband, "If you were a cat I'd have you fixed!" is all on one sour note and gets tiresome awfully quickly. On the other hand, Williams is triumphant as the raunchy waitress Helen Bedd, who dresses up for the Christmas Yard Display award ceremony by putting on a leather-fringed jacket over her uniform and slipping into those plastic heels. (You can't help noticing how shapely his calves are.) High-spirited and no-nonsense, his Helen is all gal.

Sears is larger than Williams -- roughly John Candy size -- and an expansive, genial figure. In spite of this, his most memorable characters are his quiet ones. He's quite funny as the tyrannical director, who, when his artistic decisions are questioned, points out to the local yokels that "I have been to Waco." But he's even more effective as Didi's timid, henpecked husband, who receives a Christmas blessing in the form of a UFO that kidnaps him from his awful wife. And Sears's women are wonderful. Where Williams exuberantly plays female characters, Sears becomes them. His put-upon Bertha, especially, is richly characterized: small-minded but essentially decent; tough, funny and touching. When she and Arles Struvie, a local deejay, find romance in their dreary little town, they're as perfectly matched as Shakespearean lovers meeting in an enchanted forest. Love releases the inhibited Baptist Bertha: she not only fox-trots with Arles, she brazenly confesses that she enjoyed it: "I always wondered what it felt like to be a Methodist."

With its small-town setting and men playing women, "A Tuna Christmas" has a nutty, surreal energy -- it suggests what "Our Town" might be like if it were done by New York's Ridiculous Theatre Company. But the play is never merely camp. Tuna and its denizens may be funny and exaggerated, but they're not exactly a joke. Or rather, the joke is in how true they are: We laugh in recognition as well as amusement.

A Tuna Christmas, by Jaston Williams, Joe Sears and Ed Howard. Directed by Ed Howard. Set, Loren Sherman and Brad Braune; lighting, Judy Rasmuson; sound, Ken Huncovsky; costumes, Linda Fisher. With Joe Sears and Jaston Williams. At the Kennedy Center's Terrace Theater through Jan. 20.