Often It Is a Wonderful Life in Santa’s Department-Store World : His tiny clients range from beard-tuggers to doubters accompanied by Mom and Dad wielding ‘Santa blackmail.’ Still, Old St. Nick believes, and his magic endures.

Yes, Virginia, Illinois, Michigan, Massachusetts, Texas--name your state--there is a Santa Claus. The affirmative also applies to Toronto, London, Paris, almost anywhere south of the North Pole or north of the South Pole.

Santas everywhere, thousands of them--and it’s no piece of Christmas cake. The day is long, the costume hot and uncomfortable, the parents often pushy and rude if not downright abusive, and the kids, true believers or skeptics, can ask for things that would break your heart or make you laugh up your fur-trimmed sleeve.

When they aren’t yanking your beard or tweaking your cherry-like nose or poking your paunch to see if it really shakes like jelly, they might be leaving a damp donation in your lap not listed in the gift catalogs.

As visits to Santa Claus in nearly a dozen malls and department stores from Paris to London to New York to San Antonio attest, the daily grin and grind in toyland is no ho-ho-ho-ing matter.

Being a professional Santa requires the patience of a saint, as indeed the original St. Nicholas was a millennium and a half ago, long before photo opportunities with Santa were invented at an average six bucks a shot.

Just the other day, for instance, Santa in Macy’s New York beamed all over and felt a warm inner glow when a little Irish girl, with a beguiling brogue, asked him what he would like for Christmas.

“Leave me some cookies and milk, like last year,” Santa suggested.

“Oh, no, don’t you remember?” the wee colleen protested. “Last year, we left you some beer, and Mommy said you made a fool of yourself.”

Santa promised to be good this year. It had been that kind of a day. The morning’s first visitors were 31 second-graders from an inner-city school who piled on his lap all at once and sacked Santa like a rookie quarterback. He had to crawl under his throne to retrieve his steel-rimmed glasses.

Then a 5-year-old boy said the only thing he wanted for Christmas was for “my daddy to come home.”

“I get requests like that almost every day,” Santa said sadly, between swigs on a plastic water bottle like the ones marathoners use to refresh themselves over the long haul. “You never know whether the missing parent is dead, divorced or has run off. Sometimes, they want you to bring back their dog or cat or even a goldfish.”

Fred Mather, who plays Santa at the busy South Shore Plaza mall outside Boston, holds a master’s degree in psychotherapy. It comes in handy.

“This job requires tight control over the emotions,” he noted during a break “to feed his reindeer,” the euphemism for rest time from a 10-hour day in his Currier & Ives-style sleigh parked in the middle of the mall.

“Yesterday, a boy asked for a new heart for his mother. He really had me by the heartstrings. An hour later, he came back and told me she’d found it. Turns out she had misplaced a heart-shaped gold pendant.”

And now and then, the job calls for the self-defense skills of a kung fu artist.

“With beard-tuggers,” said Mather, “the trick is to engage both their hands and gently pry the fingers loose. My beard is real, and they can get snagged in it. By the end of the day, it’s a bit frazzled. I’ve tried wax and spray, but combing it out works best.”

John McFolley, a Little League football coach and retired city worker who is Santa at Detroit’s Northland Mall, was kicked in his “bad knee” by an aggressive 2-year-old. “The parents thought it was really cute, but complained to a floor walker when I nearly dropped the kid,” he said.

McFolley, 54, had an earlier jolt when a 4-year-old wound up her wish list with, “Mommy needs a husband.”

Pancho Claus, Santa’s black-bearded Latino cousin from the South Pole, visits schools and marketplaces in the barrios and housing projects of San Antonio. His reindeer answer to names like Juanito, Manuelto and Pablito.

Frank Perales, 66, has been playing Pancho for the last nine years, donning a poncho and sombrero to augment the black boots and red regalia borrowed from his antipodal cousin.

In all that time, he has “never, not once, encountered a rude, obnoxious parent or child, and I’ve gone to some real bad places. That’s how much they think of Pancho Claus. In some of those housing units down there, they kill each other every night,” he said.

Sponsored by the American G.I. Forum, a Latino veterans rights organization, Pancho has become a real hero in the barrios. Recently, a seriously ill child in one of the projects saw him on TV and asked for a visit. Frank wrapped a few presents and hurried down.

“He was 3 years old, but looked only 16 months,” Perales said. “That kid’s face lit up when he saw me in my costume. I enjoy what I do. I feel good when I can make a few kids happy.”

Like Santa, kids these days come in all ages. In almost any major metropolis, it is not uncommon for senior citizens, often homeless, to get in line for a chat with Santa and even sit on his knee.

“They come to kill a little time in their empty lives and relive for a few minutes happier days. Memories of the child that was may be all they have left now,” observed Macy’s New York Santa.

Several days a week, Bill Fleming, the Santa at Toronto’s bustling Eaton Center, is visited by an almost toothless man of about 30, dressed all in black. They exchange greetings. Santa offers a candy cane. “No, those are for the little ones,” the mystery man says and quietly moves on.

At Marshall Field’s in Chicago, Keith Skilling, a graduate student at DePaul and three-year veteran Santa, had a 30-year-old male come calling with his fiancee and 30 members of his family.

“And what would you like for Christmas?” Santa ritually asked.

With camcorders grinding, he turned to his beloved and soulfully said: “I’d like you to marry me.” She whispered assent, but Santa, claiming he was “getting deaf,” made her say it louder for the soundtrack.

Earlier, Skilling confronted another family situation when a child asked for triplets.

“Maybe you should talk to Mommy and Daddy,” Santa nervously ventured. A floorwalker dashed up and whispered that “Triplet Babies” was the name of a popular toy. The jolly old elf sentenced himself to an after-hours tour of the toy department to avoid future embarrassment.

The transit strike in Paris leaves the 22-year-old Santa at the Printemps department store pretty lonely without tiny clients. But in London, they queue up for three hours to see his counterpart at Harrods.

By Christmas Eve, 50,000 British children will have curtsied at his Knightsbridge throne, including some royal princes and princesses from the nearby House of Windsor.

One thing is universal: Santas everywhere deplore parents who bully a child into smiling for the camera or engage in what Fred Mather at the Boston mall calls “Santa blackmail--’If you don’t stop bawling, Santa Claus won’t come to our house. Isn’t that so, Santa?’ ”

And almost every day, he adds, “when a kid asks for an 18-speed bike or heavy metal trap drums, there’s Mom or Dad in the background shaking their head like a pitcher refusing a catcher’s signal for a curve ball.”

All the Santas interviewed deal almost daily with doubters and skeptics. “I’ve had kids proclaim, ‘I don’t believe in you; Mommy made me come,’ ” said Macy’s New York Santa. “I look them in the eye and say, ‘But Santa believes in you.’ It shakes them a little.”

In London, where the rooftops bristle with Dickensian chimney pots, Harrods’ Santa often is grilled about how he keeps his white beard and red plush rompers soot-free while dropping into fireplaces.

But for most, seeing is believing.

Boston’s Santa had just settled on his knee a Cambodian tot in a candy-striped snowsuit and Red Sox baseball cap when the P.A. system broadcast an alarm for a similarly arrayed lost child.

“Your parents may be looking for you,” Santa said.

“I ran away to see you,” the fugitive confessed. “Mommy and Daddy don’t believe in Christmas.”