At first glance, it appears there are only two men in the room--one slim and ferretlike, the other a big round fellow with a sweet, pillowy face. But sit down for a chat with Jaston Williams and Joe Sears--the creators and stars of the hilarious, home-fried theatrical trilogy "Greater Tuna," "A Tuna Christmas" and the current "Red, White and Tuna," now at the Kennedy Center--and before too long a host of others have horned in on the conversation. They all hail from the fictional burg of Tuna, the third-smallest town in Texas. One's more of a fruitcake or troublemaker than the next. And each has a crystal-clear agenda.

Here's inhibited, martyrish mother of three Bertha Bumiller (channeled through Sears) talking about her fiance, Radio OKKK deejay Arles Struvie: "I'm all in favor of Arles, but he has a lot of bad habits that are real hard for me to put with. He has this cat named Pinky. I hate cats. I've always hated cats. They can suck the breath right out of a baby. And he won't go to church. That's real hard for me because I'm used to the third pew every Sunday."

Retorts Struvie (channeled through Williams): "Those Christians scare me cuz they hate ya, and they hate ya in a real Christian way."

Now it's Bertha's whiny daughter Charlene (Williams) who pipes up:

"My husband's defending our country in hostile outposts while I'm about to have his baby here!"

"He's flippin' hamburgers in Guam," Bertha explains dryly. "Worst thing could happen to him is a grill burn."

"When he gets back and after I have the baby, we're gonna move to Bakersfield. I hear it's like paradise."

Just how far along are you? a reporter asks Charlene.

"She's just about ready to drop it," sighs Bertha. "Gotta keep her on the linoleum."

Sears, 49, and Williams, 47, crack up. Even after 18 years of living inside these and 21 other characters' heads, the two still chortle at their creations' off-the-wall utterances. What began as an improvised sketch at a friend's party by two young Austin-based actors has gradually developed into a cottage industry.

In addition to the extensive touring that Sears and Williams have done over the years, the first installment of the trilogy--written with the invaluable Ed Howard, who also serves as their director--has become one of the most frequently produced plays in the country. "Greater Tuna" was turned into an HBO special by Norman Lear. George and Barbara Bush invited the pair to perform at the White House. Sears was nominated for a Tony Award for best actor when they played New York. There's even a Tuna Little Theater in Austin, featuring performances year-round with a cast trained by the masters. Tuna baseball caps, tote bags and T-shirts can be ordered by calling a toll-free number or going on the Internet.

"The first show was done on a tape recorder," recalls Sears, the more introverted and soft-spoken of the duo. "We did a lot of improvisation, based on the news of the day. By the time we got around to 'A Tuna Christmas,' we began to go off and write things down, do individual scene work. Writing is difficult. It's based on what you can contrive, yet that's the very thing you have to avoid. And these days, it's getting tougher and tougher to be a satirist."

"So much has changed, so much has come and gone," muses Williams, whom Sears fondly refers to as "one of a dying breed--a dyed-in-the-wool Texas liberal."

Williams continues: "In the early '80s, we were going directly at the Moral Majority, then reached a point when Clinton first came in, where we'd done that story and it didn't apply anymore. And then, two years later, Newt Gingrich made it all relevant again."

Adds Sears: "I've referred to 'Greater Tuna' as our political weapon. We haven't had to bring it out for a few years, but you never know who's going to follow Newt."

The way Williams sees it, "Greater Tuna" dealt with politics, "A Tuna Christmas" with relationships, and "Red, White and Tuna" with change. The new show, in fact, centers on the Tuna High class reunion, a fierce campaign to elect the Reunion Queen, and the introduction of two new characters, Amber Windchime and Star Birdfeather (who changed their names from Fern and Berenice), who have traveled all the way from Lubbock to revisit the scene of their unhappy girlhoods.

"Star's real partial to Lubbock because she made love for the first time there during a tornado, and she's been trying to re-create the experience ever since," says Amber (Williams) in blissed-out, cosmically connected fashion. "The walls really did blow away!"

"Those two left because they were a bunch of misfits!" interrupts Leonard Childers (Sears), one of Tuna's redneck blowhards.

"Oh go eat some raw meat, you fascist!" counters Amber.

When Williams surfaces from Amber and Star's tie-dyed realm, he laments the changes that have wreaked havoc on the kind of small-town life celebrated in the trilogy. Especially West Texas small-town life, of which he is a product--he grew up in a place called Crosbyton--and a dogged scrutinizer.

"It's a hell of a fraternity to belong to," Williams says. He reminisces about his recently departed mother, "one of the toughest, funniest and occasionally meanest people I've ever known"; his brother, who "talks like Yosemite Sam"; his mother's best girlfriend, a pilot with emphysema who had to stop smoking for months every time she wanted to fly (something about the oxygen); and that lady's son; and a hairdresser who worked in the big city but regularly came back home and fixed all the women up with identical helmet hair ("you need it, what with that wind!").

Listening to Williams, it's easy to understand the source of all those Tuna characters sporting bouffant dos and flowery dresses and iron wills. Sears's influences aren't that far removed; he grew up in Bartlesville, Okla., surrounded by ranchers and cowboys and many aunts whose speech and mannerisms he absorbed like a sponge and then made his own.

These days, the pair make their homes in radically different settings--Sears on a ranch in Wyoming, Williams in the French Quarter of New Orleans--but they're still on the lookout for the eccentric gesture or conversational pattern. Both places, notes Williams, are chock-full of notable characters, and "we share them with each other--some wild mountain man, or some guy dressed in a two-piece bathing suit handcuffed to a pole outside my house. You take the material where it comes."

Will there be another chapter in the Tuna saga? It's not very likely. Sears talks about taking the whole trilogy to London's West End, where people like that sort of marathon event. Williams jokes about a sequel titled "Escape From Tuna" in which all those folks who've gotten out vent and dish while stretched out on a psychiatrist's couch.

Actually, the Tuna Twosome are pretty happy about their latest vehicle.

"I think it'll make for fine closure," drawls Williams. "And then we can take off the high heels for a while."

CAPTION: Joe Sears, left, and Jaston Williams in "Red, White and Tuna."

CAPTION: Jaston Williams (the smaller of the two) and Joe Sears at the Kennedy Center: The "Tuna" guys make it their business to gleefully cross the line.