It all started with four agents, a station wagon and a dozen boxes of client files spirited out of the ICM offices in the middle of the night — and returned hours later under the threat of having the law sent after them.

Endeavor bowed with a bang after word spread of the infamous office-clearing by a quartet of ICM TV and lit agents on March 28, 1995. That audacious move by Ari Emanuel, David Greenblatt, Rick Rosen and Tom Strickler earned a banner story in Daily Variety (“Secret Agents Defect in the Dark”).

But after the drama subsided, the agency had its humble beginnings in an office above an Islands restaurant in BevHills. At the start, the financing for the company came from credit cards, second mortgages and a short-term loan from a friendly producer.

The company’s key clients were mostly TV writer-producers — not the sexiest side of the talent rep biz at a time when the caste system for creatives working in film versus TV was far more pronounced than it is today.

Fourteen years later, Endeavor’s rags-to-riches success story was completed by the deal reached April 27 for it to merge with showbiz’s oldest tenpercentery, William Morris Agency. It was with only a little exaggeration that some biz insiders described the deal that will create WME Entertainment as: “Endeavor just got a whole lot bigger.”

Others were marveling that a company still in its adolescence could grow to hold its own in a merger with the 111-year-old stalwart that has been involved in every aspect of showbiz since vaudeville.

While there’s no question that Endeavor has the goods in terms of clients, the company’s carefully tailored image and the intangible heat factor has also played a big part in its rise.

The epitome of Endeavor’s image-polishing is HBO’s “Entourage.” Does it matter from a bottom-line perspective that viewers far outside of L.A. know that Emanuel is the inspiration for the show’s alpha-agent character Ari Gold? No, but it doesn’t hurt, either.

What’s more important for the agency inside the biz is the knowledge that “Entourage” was a project assembled by Endeavor on behalf of its client Mark Wahlberg, who wanted to produce a series about his experience as a rising star. The success of the show, created by Endeavor-repped writer Doug Ellin, put Wahlberg and his manager-producing partner Stephen Levinson on the map as producers.

Endeavor is known as a hive of young, aggressive agents who are encouraged to think like entrepreneurs in generating opportunities for their clients. (What’s good for the client is good for the agency too.)

It’s hard to quantify the value of a company’s culture on a balance sheet, but the Endeavor ethos is prized by agency insiders. And it was viewed as an asset that Endeavor brought to the table in the merger discussions with WMA. Emanuel is taking the operational reins of WME as co-CEO with Patrick Whitesell, who has run Endeavor alongside Emanuel for the past few years, and WMA’s Dave Wirtschafter.

As WMA and Endeavor meld their operations, the questions of who stays and who goes will be determined in part by whether WME’s toppers feel the person will be a good fit, culturally speaking.

But cracking that code may be hard for those from the WMA side. Many at Endeavor have grown up at the agency, going back to the days when the smell of french fries from the restaurant below would fill its offices every afternoon around 3 p.m.

“Culture emanates from the top,” says Rosen, who will run WME’s TV operations. “It’s something we’ve always emphasized — the notion of having an entrepreneurial spirit and an aggressive attitude toward representing clients is ingrained in everybody who works here.”