“Survivor: All-Stars” stages its supernova Sunday, as the tribe — called Sha-boom Sha-bonga, or, as always, something equally ridiculous — narrows the field of four down to one.

CBS promises “a surprise so big, it will stun everyone.” And Donald Trump has absolutely nothing to do with the show.

Of course, the surprise is a secret in a series fueled by so many secrets that CBS isn’t even saying exactly when, during the 7 p.m.-to-10 p.m. extravaganza, the tribal tribulations will end in Panama’s dank jungles and the action will shift live to New York’s Madison Square Garden, where we find out who wins the $1 million.

But in a conference call with TV critics, swell “Survivor” host Jeff Probst promised that the big “reveal,” as they call it in the reality TV biz, “will definitely have people talking.”

“Survivor,” now a fixture on the TV landscape, doesn’t do that much anymore. As the series unfolds, addicted fans can TiVo or tape, and watch several nights later without worry that some radio talk show or newspaper headline will spill the beans about who got the boot.

The show is not hot, but it is a major hit. “Survivor: All-Stars” ranks fourth this season among 195 prime-time network shows. But the thing is, last fall’s “Survivor: No-Stars” installment ranks fifth, tied with the Thursday night “Apprentice.”

“I don’t think the show attracts the casual viewer,” Probst said. “You’re either in or you’re out. I didn’t think for a second that another 50 percent would come in and watch because it’s the all-stars. Nor do I think the audience will dip for Season Nine.”

The 21 million fans who are in — the number has barely fluctuated since Season Two — already know that the new stuff starts taping next month in an as-yet-undisclosed location, for broadcast in September.

Probst says he can’t wait to get back to the rookies.

With all-stars, “you’re guaranteed the best reality people, who will always give you gold and are hilarious,” he said, “but I would vote never to do it again. … The game is better played by strangers.”

Castaways, from left, Rupert Boneham, Amber Brkich, Rob Mariano, and Jenna Lewis on Contadora Island, Panama, appear on CBS' Survivor:

Early exiters on “Survivor” fade to black. And only one person, “The View’s” Elisabeth Filarski Hasselbeck, has found stardom outside the show. But for those who make it five or six weeks, “Survivor” can cause permanent life changes.

Some changes are superficial. Kathy Vavrick-O’Brien is still a Realtor in Vermont, but she has kept off the weight she lost on the Survivor Diet, and, with the help of stylists, has morphed from dowdy to hottie.

Other changes are transformative. With her fourth-place winnings from the original “Survivor,” Sue Hawk was able to escape wintry Wisconsin, where she worked as a truck driver, and buy a smoothie store in Las Vegas.

On “Survivor: All-Stars,” Hawk had a meltdown and became only the third person in “Survivor” history to quit, after Richard Hatch, who elevated nudity to a survival strategy, rubbed against her inappropriately in a challenge game.

Sultry Jenna Morasca was the second quitter, three weeks earlier. With the $1 million “Survivor Six” first-place check already tucked into her bathing suit, she left to be with her dying mother.

Previous experience does not necessarily discourage perseverance. The four finalists who face off Sunday have all gone further than they did their first time. And, for 36 days in the jungle, they’ve also already earned considerably more than any of them made in a whole year before “Survivor.” Even the fourth-place finisher will win more than the $100,000 traditionally reserved for second place.

This game’s second prize is $250,000, and that windfall may influence endgame play.

Probst knows who has made it to the final two, because the challenges and votes happened months ago in Panama. But, unlike his boss, Burnett, who tries to mislead fans, Probst always tries to answer speculative questions honestly, from the perspective of what he thought before the events unfolded.

Probst said his favorite was construction worker Rob Mariano: “This is the blue-collar dude from Boston, three gold chains, tucks a girl under his arm, builds a shelter for her, and then annihilates the others. And in the jungle? That’s romantic.”

Suspecting that the “girl,” Amber Brkich, has instilled less animosity in the jury of eliminated contestants that will pick the winner, Probst isn’t sure Rob’s strategy will carry the day.

“This is a really complicated social game,” he said. “How do you vote off people who you are living with, and then do it in such a way that when they come back, they’ll vote to give you $1 million?”