For Comedian Jeni, It’s Still Showtime : Stand-up: Cable specials allow him to develop bits and have given him fans who want to hear their favorite hits.

Richard Jeni, the streetwise comedian once described as “the illegitimate son of Robin Williams and Bruce Willis,” has been on a roll since he made his first appearance on “The Tonight Show” in 1988.

Not only have his fans nominated him twice (’88 and ‘89) for an American Comedy Award as the Best Male Comedy Club Performer, but he was named Comedy USA’s Best Nightclub Comedian in ‘89, an award voted by comedians and club owners.

Even more important than his frequent guest shots on “The Tonight Show” and “Late Night With David Letterman” have been his two Showtime comedy specials, which allowed him the luxury of more air time to do what he does best: develop themes and spin extended anecdotes on everything from “The Brady Bunch” to anti-cigarette campaigns.

The high-visibility specials “definitely had an impact,” acknowledges the Brooklyn-born comic, who will be at the Irvine Improv Thursday through Sunday. “It changes in the sense that once you start getting a following, the people are there to see you. It’s a whole different story when people are there to see you than when they just come because the sign says ‘comedy’ on it.

“It makes it a lot easier, actually. You don’t have to talk the audience into believing you. They believe you already. If the audience expects that you’ll be funny--that they’ll be entertained--it’s much easier.

“The other thing is they shout out requests now: ‘Do this bit, do that bit!’ ” Are they asking for his set-piece on “Jaws IV”? Or his routine about how his father didn’t have anything when he was a kid? Or his bit on how, when New Yorkers fight, they mainly only threaten a lot: “Hey! I’ll rip off your ear and stick it on your knee so any time you wanna hear somebody you’ll have to lift your knee up to their face!”

“It kind of runs the gamut,” Jeni answered. “It’s funny, when they do request something sometimes it’s too late in the show to do that particular piece of material. But the bits get to be like hit songs, and the audience wants to hear the hits.”

At the Improv, Jeni said, he’ll be doing some of the material from his most recent Showtime special, “Richard Jeni 2: Crazy From the Heat,” which aired in January. “When I first started doing specials my idea was I can’t do this material anymore, at least not for a long time,” he said. But he quickly found the opposite was true: Audiences want to hear the familiar material and walk away disappointed if they don’t.

Jeni said he looked forward to that last Showtime special, because it lasted an hour. His first special in 1989 was only 30 minutes, and he had been disappointed that he couldn’t get a lot of his material in because the routines took too long.

By the same token, he has trouble tinkering with his material “in order to get it in shape for a (typically six-minute) talk-show spot. It’s not like somebody who’s got a lot of brilliant one-liners and you stack them up until you’ve got six minutes. I sort of have to create a little mini-act.”

For the latest special, “I thought, ‘Hey, I’ve got a whole hour; I won’t have that problem.’ But when I sat in the editing room, I had a piece of material on how to cure male baldness that ran 18 minutes!”

The bit concerns those “late-night sleaze guys” on TV who say “Men, are you afraid that one day your wife will be running her fingers through your hair and you won’t be home? Well, I’m Robert Vaughn and I haven’t had a decent acting gig since ‘The Man From Uncle’ went off the air. That’s why I’m peddling this bogus hair product. . . . “

Jeni said his penchant for acting out the characters in his routines developed over time. “Basically everything that I do is just an excuse to get the jokes out, and over the years I’ve found it’s more effective to have the jokes come out of characters than just having them be spouted by me as an a monologuist.”

He said he has been influenced by a lot of comedians, including Richard Pryor and Bill Cosby. “At the beginning of my career I was trying to imitate Steve Martin for a while. Then I hit upon a novel concept of trying to be myself. But I’ve learned a lot from a lot of different comics.”

Jeni grew up in Bensonhurst, a tough Brooklyn neighborhood that’s “very Italian. We used to say if you drilled far enough down in my neighborhood you’d strike olive oil.”

The street kid went on to major in political science and economics at New York’s Hunter College before launching a brief career in public relations. He had, he recalled, “about five different jobs in a year and half. I left all of them in less than glorious circumstances. I think basically I wanted to be in show business. So what I did was deliberately screw up every job I had until I painted myself into a corner where I could go out and be a comedian.”

Jeni said it took about two years before going on stage was no longer “an absolute nightmare,” and about five years before he considered himself good. “Most comedians, it takes about five years to get good and 10 years to start getting great,” he said. This year marks his own 10th in stand-up comedy. Does he think he’s starting to get great?

He laughed, cleared his throat and said it’s up to the audience to decide.

He did allow, however, that “I am more and more satisfied personally with what I’m doing. I think for most comedians there’s always a certain amount of their act that they’re slightly embarrassed about, and that percentage gets smaller and smaller. It’s the only kind of progress I’ll admit to.”

* Richard Jeni will headline Thursday and Sunday at 8:30 p.m., Friday at 8:30 and 10:30 p.m., and Saturday at 8, 10 and midnight at the Irvine Improvisation, 4255 Campus Drive, Irvine. Tickets: $8 to $15. Information: (714) 854-5455. Jan Herman’s theater column resumes next week.