The "tenpercenters", as Variety magazine calls them, are among the most powerful people in the industry overall and it's a vicious world to survive in.
The character of Ari Gold, on popular TV comedy series Entourage, is based on the founder of the powerful Endeavor agency, Ari Emmanuel, and those who've been minced alive by Emmanuel describe Gold's character as a cuddly version of what this uber agent can be like.
His clients include Martin Scorsese, Matt Damon and Sasha Baron Cohen. His brother, Rahm Emmanuel, was appointed chief of staff by President Obama.
The agent world has typically been very macho and male dominated, but as in most industries, this has changed and women are certainly more visible these days. But this is a profession like no other, and what it takes to make it in this viciously competitive world is a curious combination of guile, cunning and literacy.
Hylda Queally, who comes from outside Ennis, is one of the most powerful agents in Hollywood, with a client list that includes Katie Holmes, Cate Blanchett, Michelle Williams and Kate Winslet.
Although she has not represented any Irish actors and in general does not participate in Irish events in LA, Ms Queally is to be honoured at a prestigious event here next month, the Oscars Wilde.
Colin Farrell and Brendan Gleeson will also receive Oscars Wilde and Ms Queally's award will be presented to her by Kate Winslet, who thanked her twice at the Golden Globes last week, after receiving two.
The president of the US-Ireland Alliance (which hosts the event), Trina Vargo, said she was delighted to acknowledge publicly the success of Ms Queally, in spite of how publicity shy she is known to be.
"Ms Queally has succeeded brilliantly in what is known to be a very tough business and we welcome the opportunity to recognise her success. I had to work to convince her to allow us to honour her, as she is a private person who is very focused on promoting those she represents," said Ms Vargo.
"But equally, one can never underestimate the influence of Irish mothers -- I think it was Hylda's mother who closed the deal for me!"
In the 20-something years that Hylda Queally has been an agent in Hollywood, she has steadily worked her way into the heart of the system, while maintaining a very quiet life.
"When I came here, I decided I would create a niche for myself and make it my own," she says. "I believe if a movie is good enough, then it will be successful.
"At the end of the day, an actor, at their core, wants to do good work. A lot of people I work with are under the firm belief that if it's not on the page, it's not on the screen."
Queally is known to be a voracious reader of everything, scripts, novels, magazines, always searching for the elusive material that will resonate with her clients.
That's why Kate Winslet singled her out at last week's Golden Globes.
It was Queally who first saw the script for Revolutionary Road when she arrived at CAA from William Morris in 2004 and immediately thought of Winslet, whom she has represented for 16 years, for the role.
Equally, she played a pivotal role in the development of The Curious Case of Benjamin Button, after the veteran Irish-American producer Kathleen Kennedy sent it to her 19 years ago.
Cate Blanchett who stars in this movie opposite Brad Pitt, has also been a long-time client of Queally's and it was at her insistence that Blanchett played the role of Bob Dylan in last year's superb I'm Not There.
"It's a certain luxury when one's acting ability is unparalleled and it allows incredible freedom as an agent and an actress to say, 'Let's do something a little bit different', where the guarantee isn't written in at the end, but it explores muscles you could never use in the theatre world," said Queally.
So what does it take to become an agent like Queally?
"You have to be absolutely indefatigueble", says former Hollywood agent John Lyons, who comes from Tuam.
"In terms of time and energy, the higher up you go in the list of star power, the more you simply have to be available to your clients.
"The best agents, like Hylda, are very literate and able to read a good script and match it to their clients' strengths -- that's what really separates the men from the boys. You really have to know your clients inside out.
"You also have to be multi-faceted, sometimes you are like a parent, a caregiver to the client; at other times you have to be like a lawyer and able to discern bigger potential problems. You also need a certain degree of ruthlessness."
Lyons, who ran his own boutique agency for eight years, the Austin Agency, before saying goodbye to all that to become a horticulturalist, said he missed very little about the business, except maybe seeing his clients do good work.
"I found aspects of the business soul -destroying, like trying to persuade casting directors to audition your clients. Ultimately, I think I lacked the gene for ruthlessness," he said.
He says the gardening business in LA is full of former film industry people who weren't able to stand the culture of that world. Lyons himself is about to begin teaching gardening at celebrity rehab clinics in southern California.
John O'Callaghan is an actor from Tallaght who has starred in the popular television series Stargate Atlantis.
He is represented by the same agent as Jack Nicholson, Bresler Kelly, who saw him in a Conor McPherson play, Rum and Vodka in LA and signed him that night.
"You absolutely do need an agent to get any paying work in either television or even theatre," he said.
"Some people say it's the hardest thing in the world to get an agent and you do meet people who've been in LA for years and never managed to get representation."