Well, you had to expect that Jonathan Winters was going to improvise. Last night the father of improv was honored with the Mark Twain Prize for achievement in American comedy at the Kennedy Center. After a 90-minute show featuring a hefty lineup, including Robin Williams, Sid Caesar, Steve Allen and Richard Belzer, Winters was presented with the award--a bust of its namesake, humorist Mark Twain.

He regarded the football-size sculpture, turning it on the pillar that held it.

"I thank you for this," he began, "but I thought the head was going to be a little bigger."

The audience in the sold-out house, already on its feet after a prolonged standing ovation, roared.

Then, with impeccable comic timing, Winters added:

"He looks like he didn't make it through the jungle."

Perfect. When was the last time anyone had heard a headhunter joke? Winters at 73 still has the uncanny ability to nail a gag that everyone gets and everyone, it seems, thinks is funny.

Winters is the second to receive the Twain award; last year's recipient was Richard Pryor.

The parade of tributes began with Belzer, who bowed to Winters, who was sitting high above the stage in a box with his wife, Eileen, their son and daughter-in-law.

Belzer invoked Winters's most famous character, Maude Frickert, the swinging granny with the gray bun, and credited him with creating a whole generation of comics.

"There wouldn't be a Church Lady," Belzer said, referring to Dana Carvey's "Saturday Night Live" character, "if there hadn't been a Maudie Frickert."

Eugene Levy, an alum of Second City, the '70s Chicago comedy troupe, likened Winters's many characters to being in an improv troupe with several other comedians--with one exception.

"The exception being that he is the company. He is every character in the scene, and he has a mind so entrenched in characters that you actually believe each one is different. This is not only a comic genius at work, this is the epitome of character acting," said Levy. "He is the keeper of the holy grail of our craft."

When Winters, the acknowledged father of modern improvisational, character-oriented comedy, moved to New York in the '50s, he rose to prominence with appearances on "Your Show of Shows" alongside Sid Caesar and Mel Brooks, and quickly landed his own network programs--madcap free-for-alls that could have existed only in the early, format-free days of television. His groundbreaking shticks stood in contrast to the style of most comedians of the time, who were tutored in the "setup, punch line" school of Borscht Belt comedy.

He made several film appearances during the '60s--including "It's a Mad Mad Mad Mad World" and "The Russians Are Coming! The Russians Are Coming!"--but never grabbed the lead roles played by such comics as Robin Williams, who are Winters's direct descendants.

That was partially due to his reputation, Winters suspects. In 1959 and 1961 he suffered nervous breakdowns, the second of which landed him in a hospital for eight months, and he thinks he has never fully shaken the "crazy" label. Despite that, Winters was a fixture on "The Tonight Show" with Johnny Carson during the '70s and '80s, his wacky riffs leaving Carson and other guests in tears. He published a best-selling book of short stories in 1988, recorded a Grammy-winning comedy album and does occasional voicings for animated specials.

Last night's tribute--taped by cable's Comedy Central for a one-hour special on Jan. 12--featured several video clips from Winters's appearances on the Carson show, in movies and all the way back to the Jack Paar show. The audience was likely inclined to be generous with its laughter and Winters's clips, projected on a large screen, kept them rolling.

Robin Williams, a mighty exhibit of star power, was his usual frenetic self and did several turns imitating old Winters bits. He and Winters became close friends after the older comedian appeared on Williams's early-'80s TV show, "Mork & Mindy."

Williams gazed up at Winters in his box seat, and acknowledged his wife. Winters quipped back, "That's Mrs. Booth."

Finally, the honoree himself took the stage, introduced by Williams. It was no cushy assignment--not only did he have to follow a dozen top comedians, but he also had to follow clips of his own greatest hits.

He managed. In a solid 15 minutes of stand-up, Winters told stories of his return to Ohio and the rural characters he encountered there, and about a trip to a temple in Greece.

"This blue-hair turned to me and said, 'Oh, Mr. Winters, I recognized you in the temple. What did you think of the temple? Can you be serious?' "

Winters made a face that let the audience know that this woman had set him up but good.

"Well, I hate to tell you this, but I was disappointed."

"Why, what do you mean?"

"Well, everything's broken."

"But it goes back 5,000 years before Christ!"

"Well, they should have fixed it by now."

The woman turned to her husband in disbelief. Winters then slipped into the husband's voice:

"Myrna, a lot of them are completely burned out."

The Kennedy Center crowd let loose its appreciation, glad to be in on the joke with Jonathan Winters.

CAPTION: Jonathan Winters found a lot to smile about at the Kennedy Center last night.