Why does an old Jehovah’s Witness warehouse on the Brooklyn Heights waterfront have virtual golf? Why is Starbucks moving into Riverdale; why are 41 realtors moving into Williamsburg in January; and why is Ian McKellen’s King Lear cast party on Sunday in an unfinished Fort Greene condo?

It’s the spread of the Manhattan real estate empire: Our biggest firms are colonizing the outer boroughs, especially Brooklyn’s money-spinning new developments.

It’s Manifest Destiny. The brokers are coming.

“Manhattanifying: I love it—good word,” said Andrew Gerringer, managing director of the Prudential Douglas Elliman Development Marketing Group. “We get a small army of people”—meaning Elliman’s thousand-plus local agents—“and bring people across the river to the new emerging markets.”

According to outer-borough brokers, their skirmish is just beginning.

“Up until recently, Manhattan brokers wouldn’t bother coming out to Brooklyn because there wasn’t luxury product to show,” said Steve Rutter, a director of marketing for the Madison Avenue–based brokerage Stribling & Associates. “And they didn’t really have the customers for the Brooklyn product.”

Things have changed: In Williamsburg, where the lengthy list of new condos reads like bad band names (Ikon, Aqua, the Edge, Loftology, Urban Green, Sofia, etc), the Corcoran Group’s first office is opening up in the hip holy land of Bedford Avenue between North Third and Fourth Streets. Around January there will be 4,100 square feet for 41 brokers, much bigger than the area’s only other Manhattan brokerage office, Elliman, which opened a 30-agent one last year.

Eric McFarland, who will manage the Corcoran outpost, says he used to live right off Bedford “for, like, ever”—although he moved to Boerum Hill two years ago. His development-focused office has already signed up more than a dozen local projects, totaling “several hundred” apartments.

What will Williamsburg’s new agents look like? “Not dissimilar to the SoHo office or the Village office,” he said. So, considering that half a dozen Manhattan brokers have already asked to be transferred to the new office, will Williamsburg have the kind of glitzy Manhattan ambition embodied by Village luminary Dennis Mangone? (The Corcoran broker put himself on a 24-foot-wide billboard in 2004, invoking his boss’ ire.) “The question back to you is,” Mr. McFarland told a reporter, “do you think it’s not already there?”

Maybe he’s right. Philip Henn, Corcoran’s Brooklyn Rookie of the Year in 2006, left Chelsea brokering for Brooklyn Heights at the end of 2005. “Me, personally, I grew up in Manhattan,” he said from a vacation in Cabo San Lucas, “so I don’t think anything is ever too big or too much, even post-9/11.” The Henns live at the new Toy Factory Lofts in downtown Brooklyn.

Outsize brokers have outsize effects on neighborhoods. Jerry Minsky, a senior vice president at Corcoran, joined the firm when his boutique Brooklyn brokerage was bought up by Corcoran last decade. “I thought, ‘Do I want to do the Manhattan thing? Do I want to dress up for work? Let me try it.’” Now he’s known, especially on neighborhood blogs like Brownstoner.com, for serving sparkling water and caviar at real estate parties.

“I got out my suits and ties, and my sushi,” he said, “and my output tripled in volume.”

But caviar can’t beat Ian McKellen. This Sunday’s cast party for his adored Brooklyn Academy of Music production of King Lear will be in the well-coiffed ground-floor bank hall at One Hanson Place, the leggy Art Deco tower being converted into condos. The Madison Avenue–based brokerage Stribling handles One Hanson sales, so the firm is sponsoring the party in exchange for a few tickets to the final performance and party.

“We’re obviously trying to lure the really high-end brokers to bring their customers to One Hanson by inviting them to this fantastic event,” a source said. The most fantastic condos in the tower go for up to $4.5 and $5 million each.

“I think Manhattan-style brokerage has come to Brooklyn,” said Mr. Minsky. “I’m proud to be a part of that. … This could be the third plateau that Jerry Minsky recollects as a monumental plateau,” he said, referring to the outpouring of new development (which follows the dot-com and post-9/11 booms). “It’s different than the first two because it’s on a more monumental scale.”

He talked to a reporter while waiting for a Sotheby’s International Realty broker, who was bringing the jeweler David Yurman to see a $3.5 million carriage house on Vanderbilt Avenue in Fort Greene. “Twenty years ago, no Sotheby’s broker would have wanted to talk to Jerry Minsky,” he said.

OUTER-BOROUGH NEIGHBORHOODS aren’t the same when Manhattan brokers or the Manhattan style settle in. Take Riverdale, where Halstead Property opened the Bronx neighborhood’s first big-name branch two years ago. Brokers spent two years calling up the corporate headquarters of Starbucks, asking the company to open up a Riverdale café. “And the reason is,” said director of sales Vasco Da Silva, “we had a lot of Manhattan buyers. … They would always ask us, ‘Where’s the nearest Starbucks?’”

So, of course, Riverdale’s first Starbucks is opening this autumn, which may very well help the brokers sell condos at the area’s six new developments, and in the three that haven’t opened yet. And then more brokers will come: “I’d say somewhere on the horizon, when there’s a critical mass of development up in that area, we’d probably look up there too,” said Mr. Gerringer from Elliman, talking about the Bronx.

Even Brown Harris Stevens, the well-heeled Manhattan firm that goes back to 1873, is adding 2,500 square feet to its Brooklyn Heights office and doubling its Park Slope branch this year, according to executive vice president Chris Thomas. But he said that Manhattan ostentation doesn’t necessarily spread when Manhattan brokers move into new neighborhoods. “That kind of flamboyance is less likely to play well in the Brooklyn marketplace, simply because the orientation of the marketplace is different.

“It’s more focused on what the play-dates are going to be than which new development has the best hors d’oeuvres, or who’s giving out the best goodie bags.”

Mr. Minsky invests more passionately in Manhattan’s realty sheen. “When you’re selling something for the prices I’m selling for, serving things at your open houses, which I’m known to do, and doing a bang-up job, it is par for the course.”

Likewise, executives like Mr. Rutter from Stribling think up golf simulators, teenage video-game rooms, and yoga centers for developments like One Brooklyn Bridge Park (now luxury lofts, once a Jehovah’s Witness center).

“We’re not saying that if we didn’t have these things the buyers wouldn’t come,” Mr. Rutter said, “but when you’re competing with other projects and trying to provide as many amenities as you can, anything that gives a project an upper hand is what we’re trying to do. … That’s a Manhattan mentality, but we’re starting to see that more.”

“Now this is all new stuff to Brooklyn over the past three, four years,” said Mr. Gerringer from Elliman. “That’s why there are a lot of offices opening up in the boroughs, and you’re going to see a lot more offices.”

ELIZABETH STRIBLING HASN'T OPENED one of her namesake offices in the outer boroughs yet, although in about a year she’ll move into a 5,600-square-foot One Brooklyn penthouse. “I’ve got my decorator flying over from Paris,” she said. “We’re going to buy some swell antiques.”

More than Parisian decorators, according to Ms. Stribling, the revolutionary change in Brooklyn real estate has been the acceptance of co-brokering.

“That’s the elephant in the room,” she said. She was referring to local agencies that traditionally haven’t (and sometimes still don’t) share their listings with other brokerages, but instead try to reach buyers directly.

So when big-firm Manhattan agents list properties in the outer boroughs, they’re instantly casting a wider net. “I think the larger projects are better represented by firms that have a presence in Manhattan,” Mr. Rutter said, “because it’s important to bring these Manhattan customers and these Manhattan brokers out to these projects.”

The president of independent Park Slope agency Warren Lewis, Marc Garstein, might even agree. “I really think the big impact is they are exposing people to Brooklyn who were otherwise not inclined to look. Are they good or bad? It’s taste and opinion.”

The Brooklyn Chamber of Commerce doesn’t have statistics on the number of Manhattan agents spreading to Brooklyn, although its communications vice president, Leticia Theodore-Greene, had this personal opinion: “I remember when I was looking to buy in Brooklyn, I had to go to a broker’s Manhattan office, which pissed me off.”

A Manhattan-based broker like Stefan Hiller wouldn’t apologize. He works out of Prudential Douglas Elliman’s West 17th Street office, yet he just became an on-site agent at the luxury Powerhouse condo in Long Island City. “Why shouldn’t I go?” he said about his treks out of Manhattan. After all, it’s a quicker train ride than his trip to the Upper East Side.

But will it matter to Long Island City if its $1 billion Silvercup Studios project, or its 74-acre Queens West development, is marketed by out-of-towners? Will the neighborhood be soiled if Manhattan brokers bring in golf simulators and a Starbucks and head-shot billboards? “Everybody promotes themselves,” said the independent DUMBO developer David Walentas. “It’s America.”