A mere 25 years ago the No. 1 comedian in television made a nation laugh by saying things like: "I'll kiwl you, I'll kiwl you again, I'll kiwl you a miwllion times." He walked on the sides of his shoes and we fell on the floor.

Television has come a long way. Today the No. 1 comedian makes America laugh by saying: "nanoo," "shazbot" and, "oh wow, reality! What a concept!" He twists his ears and sists on his face and we roll in the aisles.

This weekend these two one-man eras, Milton Berle and Robin Williams, both came to New York and made it the comedy center of the universe. Berl, 70, hosted "Staurday Night Live" from Studio 8-H at NBC in Rockefeller Center, two floors up from Studio 6-B where he held forth as king of all the airwaves a quartercentury ago.

And Williams, 26, concluded a soldout, six-night stand at the Copacabana nightclub, wher an army of audio engineers recorded material for a Casablanca record album due out later this year and certain to go double platinum or maybe, as the Wall Street Journal currently puts it, "titanium."

On top of that, his salary for playing Mork on ABC's "Mork and Mindy" has been doubled for next season-from $15,000 to $30,000 a week-and he is set to play the lead in "Popeye," with Shelly Duvall as Olive Oyl, in a film to be directed by Robert Altman next January.

So no wonder New York has gone Robin Williams crazy. His appearance at Studio 54 one night sparked a near riot. The whole Copa run sold out "like that," said a waitress who snapped her fingers and then complained she couldn't even get tickets for herself. They were being scalped on the streets for up to $100 spiece. And Williams' elfin little face keeps floating by on city buses displaying ads for a local magazine with himself on the cover.

There were hopes that the eras would meet-that a Mork and Miltie show would develop at a party after "Saturday Night Live" left the air-but while Mork showed up at the drab midtown bar, Uncle Miltie did not. These two comedians may be of entirely different generations, traditions and styles, but they both use a blitzkrieg technique on their audiences.

With Williams it's a stream-of-consciousness approach which is remarkable not for the funniness of the jokes-he tells virtually no jokes-but the dizzying profusion of references.

Robin Williams really is like a man from another planet who has absorbed our entire culture from afar and has just arrived to play it all back for us at 120 beats per minute-and not necessarily in its original order.

One moment he is on his knees as all of the midgets from "The Wizard of Oz" singing, "We represent the William Morris Agency" and the next he is the title character of "The Fly" screaming in a wee voice, "Help me, help me," and the next he flashes forward to a reminiscence of World War III which lasted 45 seconds and was preceded by a presidential address from Jimmy Carter: "Thank you very much. You're on your own. Good night."

Williams even projects himself into his own distant future as a has-been telling it all to an invisible bartender: "I used to be on Tee Vee. Ninny niny. I was on every damn magazine cover but Ebony and Popular Mechangics." Then he becomes a "memory tape" of his past: "Mrs. Williams, I dropped the baby-I don't know why."

Or Mickey Mouse: "Look what they did to Goofy-they gave him a frontal lobotomy!"

Or "Rev. Ernest Angry": "Can I get an 'amen'?" "Amen." "Can I get a woman, too!"

Or Albert Einstein's ghost showing up at Three Mile Island: "Vot are you doingk with my formula? I little words and dis is vot happens?"

Williams is at the center of an overcrowed room but in a way he has the audience surrounded. When he fails to get the response he wants, he says, 'Ohhh, comedy hell," but when they laugh very loudly he may gasp, "Ohhh, comedy heaven." And if they get too carried away, he says, "You're laughing at nothing now."

Before the show begins technicians in blue jeans run about frenetically carrying such mechanisms as a pair of suspenders that have been wired for sound. Williams will also wear a coat that has been wired for sound and even a little plastic pin that has been wired for sound. And all the little wires go to great big wires and the great big wires go to a giant sound truck parked outside the Copa.

The audience Friday night included not only the evanescent and ubiquitous Andy Warhol but a delegation of new-generation comedy talent from "Saturday Night Live"-Gilda Radner, Andy Kaufman (now of "Taxi"), Bill Murray and his brother, writer Brian Doyle-Murray-all of them crowded into Williams' dressing room backstage where after the snow he waa discovered in a gaudy Hawaiian shirt he explained as "a history of color." He seemed quiet and calm, as if someone had just removed the electrodes from his temples.

"Your cheese is better than ours," said Radner, cutting hereself a slice of cheddar while Williams posed obligingly for SX 70 photos.

One celebrity did not come backstate. Veteran comic of the old school Joey Adams had watched Williams with a blank expression and no laughter finally, apparently baffled, Adams walked out of the show before it ended.

He didn't get it.

Almost everybody else, much younger than he, did; they watched Williams improvise, change course and flip-flop perspectives with as much amazed rapture as a ballet crowd savoring Baryshnikov's daring leaps.

Comedy is really structured lunacy and Williams tries to use as little structure as possible. He is a dazzler.

But over at "Saturday Night Live," when it's still Saturday afternoon, a past master and a legend in his own time and as many other times as possible, Milton Berle is not quite clicking the way it was hoped as he rehearses sketches for the night's show.

In his office above the studio, producer Lorne Michaels points at a TV monitor on which Uncle Miltie, in a frightwig, is rehearsing. "Look at that," says Michaels. "This is supposed to be kind of a touching scene, and he wants to know why can't he put a cigar up his nose."

"See," Berle is saying to the director, "this way we can get two laughs here instead of one."

Billy Murray bursts into Michaels' office. "You want to know where this sketch is going?" Murray asks. "It's going one way: Down."

Berle arrived at the first rehearsal on Monday with high praise for the four-year-old smash hit late-night series: "Yeah, I saw it once," he told Michaels. He referred to the cast as "the stars of tomorrow."

"But what he didn't realize," Michaels says later, "is that they're not the stars of tomorrow. They're the stars of today, and he's the star of yesterday. He is probably the most professional man in that studio. But he doesn't realize that sometimes we're dealing with attitudes, not just with getting laughs."

Berle taped a promo for the show in which he was to mention the musical guest, jazz man Ornette Coleman. Berle said ". . . and musical guest Ornette Coleman"-then paused, looked off, and added: "Who's she?"

Ornettee Coleman's manager did not find that very funny.

Berle's opening monologue was considered very "Las Vegasy" by many on the show. A Williams sex joke might begin: "Let's read pornography to the flowers and get them excited." A Berle sex joke would be something else again: "I was in bed with my wife the other night and she said, 'Gee, even an egg takes three minutes'."

Of all things, Berle joked about age: "George Burns is so old he was circumcised with a stone knife." Or: "I just got back from Miami Beach. I wouldn't say those people are old, but the average age is 'deceased.'"

Later, Berle used lines at least 20 years old to recall how he was beaten in the ratings in the '50s by Bishop Fulton J. Sheen: "Of course he won-he had better writers." Or: "We both had the same sponsor-Sky Chief." About the only thing Uncle Miltie didn't resurrect was "Good Everning, Ladies and Germs."

Yet everyone is in awe not so much of Berle's status as a fire-breathing icon but at the way he thrown himself into this show as if he were their age and it was his opening night on TV.

"He has so much energy, he's like a puppy," says writer Don Novello, sometimes Father Guido Sarducci on the show.

"He's got an anecdote for every WORD," marvels Brian Doyle-Murray.

They all acclaim him for working so hard when he really has nothing left to prove. But comedians are people who always feel they have something left to prove. The ultimate comedian would probably end his act by murdering his audience with a machine gun to make sure none of them would ever laugh louder than they had at him.

When Williams tells his audience at the Copa, "show business is my life," it gets a laugh. The new comedians ridicule the idea of show-biz tunnel vision and self-glorification.

But when Uncle tells the audience at NBC, "show business has been my life," it is one of his few straight lines. Appearing from backstage during a commercial break, Berle gets a spontaneous, loving hand from the audience. He tells them to save it until they're on the air and the country can hear it too. "You can applaud when the music starts, or when the camera discovers me," he instructs them.

The Saturday Nighters do not consider the Bere show a success when it has ended. They are embarrassed by Berle's sentimentality and his performance of "September Song," because this is the kind of old hat hamminess they like to lampoon.

Asked for his view of the program, one of the writers says. "It bit it."

These youngsters, as Ed Sullivan would have called them, have sentimental streaks, but they tend to be pretty narrow, and reserved for heroes of their own time-not their moms' and dads'. Many of those in the audience Saturday night-young adults, not tots-were not even bon when Uncle Miltie began his reign of comedy terror. And yet to be ungrateful for the groundwork he so bravely laid is-to borrown an image from Williams-like the engineers at Three Mile Island telling Einstein to go away and mind his own business.

One also must envy Berle his dauntless bravado. When an 36-year-old woman approached him early in the week and claimed she had watched him when she was a little girl, he told her. "Go to hell."

"Staurday Night Live" actually continued until 8 o'clock Sunday morning for many of the show's writers and performers, who ended up way downtown at an unspeakably grungy bar operated privately for their amuseby John Belushi and Dan Aykroyd, two of the stars of today. The Murray brothers had flown in a brother and sister and their sweet old Irish mother. Lucille, from Chicago, and very early Sunday morning, Mrs. Murray and Belushi could be seen jitter-bugging on the dance floor to Elvis Presley's recording of "Jailhouse Rock."

Williams, exhausted, all but melted down, had long since called it a night, but the words with which he left his audience at the Copa still hung invisibly and spiritually in the air. He had pointed to his heart and said. "Just a little bit of madness keeps you alive."

There was a lot of madness in New York this weekend, and the city was as alive as it could be.

Ohhh, comedy heaven. CAPTION:

Pictures 1 and 2, Milton Berle in the 1950s and Robin Williams as Mork.; Picture 3, Robin Williams as Mork.; Picture 4, Milton Berle with Laraine Newman, left, and Jane Curtin, AP