All of that is in keeping with the spirit of the HBO show, which never hid from the warts, blemishes and personal and business failures of its characters. Mr. Chase wound up in drug rehab, as his career rose and fell. Mr. Gold was kicked out of one agency, founded another, and lost his wife, at least temporarily, to the celebrity chef Bobby Flay before the eighth season wrapped in 2011.

Image Ariel Emanuel, one of the high-powered talent agents on whom the Ari Gold character of “Entourage” was based, in 2012. Credit... Alex J. Berlinerm/ABImages, via Associated Press

Calling Mr. Flay his sworn enemy, Mr. Gold said “it will be agent meets fist” for anyone who dared to dine at or recommend a Flay restaurant. (Mr. Flay is currently having real-life marital woes of his own.)

Mr. Emanuel, who represents Mr. Wahlberg, is still an agent. But in the real world, he and Mr. Whitesell now spend less time wrapped in the antic lives of their movie clients and more on the corporate complexities that came with their $2.4 billion deal last year to merge W.M.E. Entertainment — which had been formed by the merger of their Endeavor agency and William Morris — with I.M.G., a sports powerhouse based in New York.

A spokesman said Mr. Emanuel was declining interviews touching on the “Entourage” film, but Mr. Ellin said he had watched the new film several times. “Ari loves it; he was with me in the editing room,” said Mr. Ellin.

In real life, the agencies’ corporate structures have brought corporate behavior, which has posed a challenge for Mr. Ellin, who had to work a little harder to find the fun in chronicling it.

“You need to act a little bit more businesslike, a little more Wall Street,” said Gavin Polone, who was once an agent at International Creative Management and the United Talent Agency and now produces for film and television.

A veteran of the glory days, Mr. Polone was fired twice from agency jobs, but he sued and wrangled a $6 million settlement from the second of those incidents. “If you’re a young agent now, you’re not going to make the kind of money I was making when I was 28 years old,” he said in an interview last month.