Twenty-five years ago a kindly children's book writer in Belgium found himself at the dinner table and momentarily at a loss for a word. "Pass the uh, uh...schtroumpf (Flemish for whatchamacallit)," he said. "Hmm," he repeated to himself, "schtroumpf." Salt was what Peyo had in mind Culliford had in mind, but he would soon get a good deal more than he asked for. Rooted in his imagination, the nonsense word gave birth to a race of four-fingered blue trolls in white bonnets who, in turn, begat an internationally best-selling series of 25 books - and now, with The Smurfs (English for the Schtroumpfs), the top children's television show in America.

The cartoon company Hanna-Barbera reports that The Smurfs - featured on Saturday mornings from 9 to 10 on NBC - pulled in an astonishing 44 percent share of the TV viewing audience and left CBS' omni popular Road Runner at the starting blocks for the first time in 14 years. NBC will be extending The Smurfs' reign this season by half an hour, and Culliford and Hanna-Barbera will add two humans to the cast of animated gnomes. The boys, Johan and Peewee will live on the edge of the Smurf forest, where they will join their true-blue friends In foiling the inept schemes of the evil wizard, Gargamel. Naturally, the boys will soon be fluent in Smurfese, the all-purpose argot born of Peyo Culliford's groping for a salt substitute. "Practically smurfect," they will say with kids all across America. Or, "Smurf and the whole world smurfs with you."

Smurfy's Law is clearly in effect: Everything that can go right will go right. Not only are the Emmy-nominated Smurfs a TV success to rival Disney or Sesame Street, but they are also a merchandising windfall to match E.T. Wallace Berrie, a small San Fernando Valley marketing firm, snapped up Smurf product rights before the genial, nonviolent gnomes had even appeared on TV. This year the now burgeoning company expects to sell $600 million in Smurf figurines, records, dart boards, coloring books, shoes, sleeping bags and other Smurfabilia. "I am the most surprised of all," professes Culliford, 54, who pockets a percentage of the largesse. "I've been consumed by the success of the Smurfs, and I'm working harder than ever."

One of three children born to a Brussels stockbroker and his wife, Culliford dropped out of art school after only three months when "they wanted me to draw antique heads. That didn't amuse me a bit." More inspired by American comic books, he published his first Smurf adventure in 1957 and found an audience among adults as well as children. "In Europe I know doctors and lawyers who have come home exhausted and picked up one of my books and were totally relaxed. It's a form of recreation."

Thanks to the Smurfs' success on American TV, prime-time Christmas and Valentine specials are now in the works, and Culliford travels to the U.S. twice a year to discuss scripts with Hanna-Barbera. The rest of the time he lives in a villa outside Brussels with Nine, his wife of 31 years. Their son, Thierry, 26, 1s a rock musician and amateur artist, but daughter Veronique, 28, "is an excellent secretary who draws about one picture a year," jokes Culliford.

Despite the Smurf boom, Peyo insists that neither he nor his cartoon creatures have really changed. "I have just as good a time now as I did 30 years ago," he says happily. As for the Smurfs, "they know nothing about money," he notes wistfully. "When they are hungry, they go see the baker. When they need a hammer, they borrow one. They are not part of any country, except Smurf country, Somewhere very far away.