Kaplan Fails to Make the Grade : Comedy review: Returning to stand-up, the former ‘Kotter’ teacher scores well in some areas but could try harder.

Let me tell you a story. My uncle walks into a . . .

OOOOO! OOOOO, OOOOO!

Yes, Arnold?

Excuse me, Mr. Kotter, but haven’t we heard this joke a million times already?

Yes, Arnold. But I have 35 minutes to fill here at the Improv, and not that much new material.

But then, why do the gig?

Well, because “Welcome Back, Kotter” is appearing again in syndication, John Travolta’s comeback makes Vinnie Barbarino and the rest of us hot properties, and the baby boomers all want to see if I still look like the cartoon on their old lunch boxes.

Aooooooh. So g’head, g’head . . .

(Vinnie: Comeback? I’m so confuuuuuused. )

When most of us last saw Gabe Kaplan, he was TV’s hippest teacher, sporting bell-bottoms, Afro and bushy mustache while presiding over a classroom full of sweathogs at James Buchanan High School. Since “Kotter” ended in 1979, Kaplan reportedly has spent most of his work time in the world of high finance. Now he is testing the waters for a return to the stand-up circuit where he made his mark before his TV series became such a hit.

In his brief headlining set Wednesday night, he was much the same man we remember, if pound-for-pound a little thinner in the hair department and a little thicker at the waist.

“Relax, I’m still alive,” he quipped as he arrived on stage to enthusiastic applause. And that actually might have been enough for some fans. Even his lamer moments--and there were a number of them--drew polite chuckles.

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The bulk of Kaplan’s routine these days is based on remembrances. There are stories of the “real” sweathogs, his classmates in Brooklyn who inspired the characters in his series; stories of his early days in show business, and stories detailing the family dynamic of his youth.

These tales hit, and miss, with about the same frequency as Mr. Kotter’s signature stories did on TV. Many are routine and unmemorable, but some are gems.

Most notable Wednesday were Kaplan’s impersonations of his mother and sister, affectionate portrayals infused with gentle humor and genuine life. Neither was tied to a quick punchline. The gum-chewing, Cyndi Lauper-esque sister in particular was slow to develop, but Kaplan’s patient, deliberate delivery paid off. These were the funniest and the most touching moments of the evening.

Far less successful were his Tales From a 50-Year-Old about what it was like to buy a condom for the first time, and a barely amusing segment about nocturnal emissions.

But the low point had to be his bit on “celebrity” answering machines. What kinds of greetings do famous people use? An interesting premise. But the best Kaplan could muster was a lame reference to David Letterman (“I’m out right now and here are the Top 10 reasons why”) and stale jokes keyed to an embarrassingly out-of-touch roster of names: Dr. Ruth, Henny Youngman . . . M-M-Mel Tillis, for Pete’s sake.

Next time you’re watching Nick at Nite, notice the lyric, Gabe:

Well, the names have all changed since you hung around . . . *

Gabe Kaplan performs today at 8:30 and 10:30 p.m., Saturday at 8 and 10:30 p.m. and Sunday at 8:30 p.m. at the Improv, 945 E. Birch St., Brea. $10-$12. (714) 529-7878.