When a star gets big enough, the rumours start, the stories about facelifts, hair transplants, fancy injections in Switzerland. With Benji the dog, sadly, the rumours are true: The bark has been passed to a new generation.

For the dog who arrived fashionably late yesterday for his tete-a-tete with the press, accompanied by a sizeable entourage of humans plus a parakeet named Pete, is the 2-year-old lookalike offspring of the original Benji, hereafter known as "the old man."

"We decided it was time to retire the old man, he's 17 years old; that would be 120 in human years," says Benji's trainer, Frank Inn, a portly Falsaffian type called the Stanislavski of the animal world, adding, "He was getting senile."

"Shh, don't say that, don't tell kids that," said Joe Camp, writer-director-producer and general factotum of sponded, and that seemed to be the end of it.

This dog, you will understand, is not merely a dog, is an entertainment empire. The first "Benji" film, made for $550,000, earned more than $30 million in the United States alone, making it one of the three top grossing films of 1975. and overseas, don't ask about overseas.

"In Bangkoj," marveled Frank Inn, "they had a big picture of his head four stories high." And in Japan, where the film grossed $125,000 in four days at a single theater. Joe Camp claims "you're just as likely as not to pull and have a picture of Benji on it."

If reaction in Benji's hotel is any clue, the new film. "For The Love of Benji," will be, if such a thing is possible as heartwarmingly popular as the original even if it was filmed in Greece. "Is that dog here yet, I'm just dying to see that dog," one woman gushed to a waiter, who had heard it all before: "Everyone in the hotel is dying to see him, people are stopping bellhops and asking for his room number."

One person who did to see Benji was Amy Carter, somehow squeezed into the dog's schedule between the presentation of a friendship medalfrom the Greek ambassador and a silver-engraved feeding bowl from Sen. John Tower of Texas. home of Joe Camp's Mulberry Square Productions.

As trainer Inn, a man prone to saying things like "when I worked with Arnold the pig," put the new Benji through a repertory of tricks that flabbergested mere morals and then as a reward cut tried to explain the phenomenon of the dog's success.

"People like Lassie, they liked Rin Tin Tin, but people love Benji," he says. "Everyone who sees him wants to touch him, to hug him, everyone wants to love him.Why is everyone crazyabout Farrah Fawcett-Majors?"

Benji seems to enjoy all this attention, which is just fine because for him there is no turning back. "People ask me, "Why don't you let him run out on the farm and be a regular dog?" "says Joe Camp, who leaves it to Frank Inn to explain why that would never work:

"He's a sophisticated animal trained far beyond any that I know of, but he's had such a different life. The only cows he's known are trained not to kick him; the cars he works with never run into him. In real life, these things can hurt him.

"It's like taking a guy with a college education and sending him to live in the jungles of Africa. He could'n make it."