COMEDY REVIEW : Rich Little Makes a Weak Impression : Judging by the mediocre material Sunday, he apparently figured that just showing up at the Performing Arts Center was enough.

You could feel the tension in the halls of the Orange County Performing Arts Center on Sunday night. Under orders from the headlining superstar himself, ushers cut short the intermission and rushed audience members back to their seats just minutes after the end of the opening act. Nervous Center staffers whispered among themselves about the reason the performer could keep himself from his fans no longer: “Rich,” they told one another, “has a plane to catch.”

Odds are that Rich Little caught his plane, because he didn’t waste any time coming up with material. Instead of using his facility for mimicry to any comic end, Little banked on the premise that the marvel itself was worth the price of admission.

Thus began a 90-minute shtick of celebrity voices mouthing lines about incontinence, sex organ size and patriotism; like 2 Live Crew’s Luther Campbell, Little seems to have figured out the kind of topics sure to please any crowd.

The high point of Little’s act was its opening number, “Talk Like Celebrities,” which he sang to the tune of “Talk to the Animals” from “Doctor Dolittle.” Dishing out a lyric as Groucho Marx here or Jackie Gleason there, he preserved the best element of the TV commercials and game-show appearances that distinguish his career: brevity.

With the other sketches, Little dragged out his tepid jokes over achingly long minutes, giving ample opportunity to note the dissimilarities between his impressions and the genuine articles.

When you can see Johnny Carson doing his own monologues most nights a week on television (or live, for free, at the NBC studios in Burbank), what’s the appeal of a Little sketch that seeks to do nothing but copy Carson at his most stilted?

Other overlong sketches sought to portray celebrities in unlikely occupations: Andy Rooney as a boxing announcer, Dr. Ruth Westheimer as a bank teller, James Mason as an English teacher. What could have made a mildly amusing routine of quick one-liners was instead milked like a prize Guernsey; does it really take five minutes to get across the humor of seeing Jimmy Stewart as an air-traffic controller?

For his most ambitious sketch, Little lowered a video screen over the stage to project a red-wigged image of himself as “Nightline” host Ted Koppel. The recorded Koppel acted as quizmaster for the game show “Presidential Pursuit,” in which Little played contestants George Bush, Ronald Reagan, Jimmy Carter and Richard M. Nixon.

Though he aped the patter of a famous newsman and four familiar Presidents, Little still managed to avoid his taboo areas of topicality and relevance. Nixon entered the news recently with the opening of his controversial library in nearby Yorba Linda, but this, as well as Bush’s role in the Persian Gulf crisis, budget chaos and election comeuppance, didn’t rate a mention. Instead, Little chose easier avenues of attack, giving us a Reagan who forgets and a Carter who’s an idiot.

No one expects Little to display the talents of, say, Harry Shearer, whose sketches on National Public Radio use scathing mimicry of newsmakers to underscore deviously satirical writing.

But if he plans to end his shows with a call to war (in the voice of local hero John Wayne, he demanded that Americans either pull out of the Middle East or “beat the hell out of those towel-heads”), Little should offer a bit more to think about than whether imitation is really the sincerest form of flattery.

The best bit of this evening middlebrow-beating didn’t come from Little. Credit instead goes to singer Julie Budd, whose opening act centered on a tribute to her late Las Vegas mentor, Liberace.

As slides of the entertainer were projected on the giant screen, the taped voice of Liberace spoke from beyond the grave to introduce his favorite song, “The Impossible Dream.” Budd then sang the number in an unearthly duet with Liberace, his voice adding a touch less macabre than surreal.