SO, WHO ARE the Bleacher Creatures? And how, over the past two decades, did they become this semilegendary cadre of fanatical fans who, at least in their own minds, serve as the Yankees’ secret weapon — their Tenth Man? If anyone understands them, it’s probably Bondy, who spent years sitting with them and writing columns about them before he produced his book in 2005. Rather than sticking to the usual he-said, she-said journalism, Bondy took on a Creature persona, projecting the “anarchy and mischief ” that is their hallmark.

“It took a while, but they realized I wasn’t making fun of them,” says Bondy, who also wrote this year’s Chasing the Game: America and the Quest for the World Cup. “I discovered that they are a tremendous socioeconomic mix of people, from professionals all the way down to people struggling financially. All differences are forgotten when they get to the ballpark. Within those boundaries, they become a family.”

If the Creatures are a family, then their den mother is Tina Lewis, 48. She was a standard-issue Yankees fan long before she was a Creature. At first she sat in the pricier infield seats. That changed on July 4, 1983, when for some reason she decided to buy a cheap seat out in Section 39 of the bleachers.

“It was the day of the Dave Righetti no-hitter,” Lewis recalls. “It was hot as hell. I went out to the bleachers and never left.”

What followed were some rough years for the storied Yankees, who reached the World Series only once during the ’80s and actually posted a losing record from 1989 to 1992. As a result, crowds were often sparse, making it easy for Lewis and some other hard-core bleacherites, then called “the Regulars,” to bond. Though the actual name would come later, this was the beginning of the Bleacher Creatures.

“It was general admission back then,” Lewis says. “So I had to get there early and hold seats for everybody who was coming. Can you imagine how many fights I got into over that?”

That early group included longtime fan and cowbell-banger Ali Ramirez, “the original Bleacher Creature,” who died in 1996. That year, the Yankees paid tribute to Ramirez before a game against the Seattle Mariners; fittingly, Yankees pitcher Dwight Gooden threw a no-hitter to cap off the day.

Another semifamous Creature, “Bald” Vinny Milano, found his way to the group in the late 1990s. Since 1999, his job has been to start the roll call by bellowing out the center fielder’s name. “Others did it before me, but people get married, or they get new jobs,” says Milano, who is 34. “Not everybody can make 81 home games a year.” Milano has taken his Creaturehood a step further, starting a business selling Creature-inspired shirts, hats and other paraphernalia outside the stadium and at www.baldvinny.com. “I love people, I love the Yankees, and I love being loud,” Milano says. “This brings it all together.”

Lewis, Milano and the other Creatures have enjoyed a love-hate relationship with the Yankees organization over the years. The Creatures’ antics were one reason beer sales were banned in the old stadium’s bleachers for several years, a verdict Milano considers unjust. But the suds are flowing in the new ballpark, which opened last year, and Milano and Lewis credit the front office with helping the Creatures migrate from Section 39 of the hallowed old stadium to Section 203 of the new place and for making sure they got a large bloc of season tickets together.

AS TO WHETHER OR NOT the sound and fury of the Creatures contribute to the Yankees’ success, there’s no scientific answer. But one thing is an absolute: The old Yankee Stadium was regarded by many as one of the most intimidating venues in pro sports. Not surprisingly, Bald Vinny believes the answer is clear. “We like to create the energy. If we’re loud and the players know we’ve got their back, they get amped up,” he declares.

At least a few of the players agree, even if A-Rod’s wave during the roll call seems pretty perfunctory. Yankees right fielder Nick Swisher, who plays just below the Creatures’ lair, can’t praise them enough. “They’re the best. They make Yankee Stadium what it is. They’re the essence of the stadium’s vibe. When I came over to the Yankees last year, that first time I ran out in the outfield, they welcomed me right away and made me feel right at home. They’re my peeps.”

After being released in 2008, former Yankee Jason Giambi went even further in his praise. “He said the main thing he’d miss was the Bleacher Creatures and the roll call,” Bald Vinny says. “I mean, of all the things to miss about the city of New York, he’s going to miss me and my yokel friends! That’s unreal.”

The Creatures may have their rough edges, but they embody a certain kind of brassy, unquenchable New York spirit — the kind Humphrey Bogart talks about in Casablanca when the arrogant German officer asks if he can imagine the Nazis occupying New York.

“There are certain sections of New York, Major, that I wouldn’t advise you to try to invade,” Bogart tells him.

Exactly. Starting with Section 203.