Five years ago Richard Lewis of Brooklyn, N.Y., stood on a stage in Greenwich Village and told the crowd: "I'm freaked." They laughed and laughed for the next six minutes, and Lewis, now 28, was on his way as a stand-up comic.

The rest is history. But like most history, it had to be rewritten for TV.

So Lewis, co-writer Bennett Tramer and director Gary Weis devised an artificial biography and an artificial comedian named Billy Gondola and made "Diary of a Young Comic," a pretty darn funny NBC movie to be seen at 11:30 tonight on Channel 4.

Since Lewis, who plays the title role, concedes the film is "loosely autobiographical" and since Dom DeLuise, Nina Van Pallandt, George Jessel and Dr. Sidney Garfield (the Los Angeles dentist-about-town) play themselves, the picture is obviously not wholly the fiction it pretends to be. Perhaps it is a new form of cinema that might be called "Verite Shmerite," partly because Bill Macy as Gondola's father has a habit of saying things like "Comedy, Shomedy." Among the other luminous delights of the picture is a Marilyn Monroe double from Australia, Linda Kerridge, who photographs like an alabaster baby doll and looks exactly the same in person. When he encounters this vision in the film, Gondola says. "Are you for real?" and she says. "One hopes."

When in real life albeit real life in Hollywood -- Lewis joins Kerridge for lunch, he says to her, "You're really authentically yourself, aren't you? It's purely you, isn't it?"

"Oh well," says Kerridge. "Who else can I be?"

Life imitates art's imitation of life like this all through lunch. It seems that Lewis' parents were almost as tempest-tossed by the idea of having a known comic in the family as Gondola's are in the film.

"There's no way you can tell them up front that you're going to be a comic without them thinking you're insane," Lewis says. "So I got a degree in marketing at Ohio State, all the while knowing that I was lying to them and me. If there was a degree in comedy. I would have been right there. Secretly."

Lewis, who has 60's-long hair and half-popped eyes, went from a job at Herman's Sporting Goods in New York to appearances at small clubs. At one of them, when he joshed the girlfriend of a young singer from the stage, the singer angrily cut his microphone cord with a switchblade. Eventually he made it to a regular spot on the "Sonny and Cher Variety Show," but he quit the first week:

"They made me dress up as a piece of romaine lettuce. I said, 'Sonny, iceburg lettuce maybe, but not romaine. I'm not vegetables.' I was really freaked to quit."

But he survived this disgrace and went on to innumerable appearances on the "Tonight" show and other programs. He wants to write comedy movies and he would even deign to do a series. A few years ago he approached the networks with a situation comedy about a funny college fraternity. They told him no one would watch a situation comedy about a funny fraternity.

Meeting George Jessel while filming "Diary" might have been the big thrill of his career. But it wasn't, although it was a thrill of sorts. Jessel became so caught up in the docu-comedy nature of the thing that he kept calling Lewis "Billy" even off camera.

"He autographed a picture, 'A pleasure to work with you, Billy,'" Lewis says.

"He kept going like this to me," says Kerridge, and then she mouthed silent "I love you's" with her technicolor red lips. "He said. 'Give me your phone number' and he told me I looked like one of his old girlfriends, June Haver."

"He mentioned something to the effect that the communists were very close," says Lewis. "He said. 'Forget Cuba. They're down the block.'"

Lewis has made his displaced Easterner's view of L.A. part of his act. He was the first comic to note how appropriate it is that the symbol for L.A. airport is "L.A.X." The only thing better than that might be "LUDE."

Asked whether he hates L.A. or loves it, he gives the perfect answer: "I'm ambivalent about it."

"Diary of a Young Comic" is a comfortably funny movie that suggests an early De Palma comedy but unfortunately had to be trimmed by network edict from two hours to 90 minutes. Some transitions are awkward, some scenes just sputter out, but there are highlights such as Gondola's visit to a celebrity analyst who has photos of his glamorous patients on the wall -- with black tape over their eyes to conceal their identities.

This does not prevent Gondola from recognizing such patients as Jimmy Durante, Lassie and Flipper.

In real life, Lewis does see an analyst but says he is trying to "ease out of therapy." But if he were rid of his problems, would he be a comedian any more? The mere idea shocks him into an apoplectic silence.

"Well, I'll go a couple of times a year then," he says at last. "I'll go seasonally."

He does believe himself to be terminally freaked, and therefore a slave forever to the domineering muse of humor. "There's absolutely nothing else I could think of doing," he says. "It's too late now. I'm doomed." The rest will be history in the future. CAPTION: Picture 1, Picture 2, Picture 3, Picture 4, Starring in "Diary of a Young Comic" are: Richard Lewis, above, and, top from left, Nina Van Pallandt, Dom DeLuise and George Jessel; Photos by AP and UPI .