Hollywood cliques have been around for decades.

In the 50s, the Rat Pack, with ring leader Humphrey Bogart reigned as kings of the celebrity scene.

In the 60s, the more well-known version of the Rat Pack was formed. The legendary performance group was made up of Frank Sinatra, Dean Martin, Sammy Davis, Jr., Joey Bishop and Peter Lawford, and claimed big-time celebrities like Shirley MacLaine and Marilyn Monroe as mascots.

Then in the 80s, the infamous Brat Pack came along. This group of successful, rich teen film stars, including Rob Lowe, Molly Ringwald, Emilio Estevez and Demi Moore, were best known for their hard-partying ways.

In the 90s and 00s, we had the Frat Pack, the Hollywood actors like Ben Stiller, Will Ferrell, Vince Vaughn and Owen Wilson who have appeared together in some of the most successful comedies of today.

But it’s time for the Rats, Brats and Frat boys to move over – because here comes the Pat Pack.

Since Irish acting heavyweights Colin Farrell, Gabriel Byrne, Brendan Gleeson and Cillian Murphy all signed on to bring Flann O’Brien’s classic novel “At Swim-Two-Birds” to the big screen, the group has been dubbed the “Pat Pack,” the Irish version of the Hollywood power-group.

Gleeson will make his directing debut with the long-awaited “At Swim-Two-Birds.” The novel , widely considered to be Irish writer O’Brien’s masterpiece, was first published in 1939, and focuses on a 19-year-old college student who’s fond of the drink. The young man writes a book, and thinks he sees its characters come to life.

The complicated story has three separate beginnings and endings, and will require some skillful acting and directing to come to life on the big screen.

Luckily, the film is in the hands of Irish film greats.

Not familiar with these Irish actors? Let’s take a look at the members of the Pat Pack, who’ll be coming to a theater near you in 2010.

Brendan Gleeson – the prolific Pat Packer

Gleeson, who will both direct and star in “At Swim-Two-Birds,” is a true Irish acting vet, and has been featured in countless big-name film projects since he began his acting career at age 34.

The 54-year-old Dubliner got his start in the Irish TV film “The Treaty,” in which he gave an award-winning performance as Michael Collins. He’s since appeared in blockbusters like “Braveheart,” “Gangs of New York” and “Troy,” and is the star of beloved Irish films such as “The Snapper,” “The Butcher Boy” and “Michael Collins.”

Most recently, Gleeson starred in the “Harry Potter” series as Mad-Eye Moody, and was up for a Golden Globe last year for his performance alongside Colin Farrell (who took home the award) in Martin McDonagh’s “In Bruges.”

Gleeson is nominated for a 2009 Emmy for his turn as Winston Churchill in HBO’s “Into the Storm.”

With this legendary Irish performer at the helm, “At Swim” is sure to be a hit.

Colin Farrell – the party boy Pat Packer

Brendan Gleeson’s “In Bruges” co-star Colin Farrell is one of the most recognizable (and perhaps attractive) faces to come out of Ireland.

The Dubliner, who’s as well known for his bad boy reputation as his acting skills, has starred in numerous high-profile Hollywood films, including “Phone Booth,” “Alexander,” “Minority Report,” “Daredevil,” “S.W.A.T.” and “The Recruit.”

Though he’s appeared in many American movies, the 33-year-old, who’s expecting his second child, has also starred in Irish classics such as “Intermission” alongside fellow Irishman Cillian Murphy.

Farrell’s famous face may just help catapult “At Swim” to blockbuster status.

Cillian Murphy – the private Pack Packer

There’s always the shy, quiet one of the group, and talented Irish actor Cillian Murphy fills those shoes in the Pat Pack.

The County Cork native is a successful actor both at home as a leading man in movies like “Intermission” and “The Wind that Shakes the Barley” and in the U.S. as the “bad guy” in movies like “Batman Begins" and “Red Eye” (he was nominated for a Golden Globe for this role).

But the 33-year-old keeps a low profile in Hollywood, refusing to appear on television talk shows or discuss his private life with the press.

Instead, Murphy sticks to talking about his work, including roles in hits like “28 Days Later” and “Cold Mountain.”

If this Irishman can tackle challenging roles like a transgender Irish orphan in “Breakfast on Pluto,” he most certainly can do justice to any character in O’Brien’s “At Swim.”

Gabriel Byrne – the professional Pat Packer

Not only is Gabriel Byrne a famous actor, but he’s also a celebrated film director, producer and writer.

This Hollywood pro got his start in the theater in Ireland, but quickly became a recognizable face with appearances in films like “Excalibur” in 1981, and made his star turn in the critically acclaimed “Miller’s Crossing” in 1990.

Byrne has also given memorable performances in hit films like “The Usual Suspects” and “Little Women.”

The 59-year-old Dubliner is best known for his starring role as therapist Dr. Paul Weston in the HBO hit series “In Treatment.”

Byrne has won a Golden Globe for the role, and is nominated for a 2009 Emmy. The New York Times has dubbed even dubbed the Irishman TV's "latest Dr. McDreamy.”

But the Irish actor has always stayed close to his roots. He wrote the first drama in Irish, “Draíocht,” for Irish TV in the 90s, is active in various Irish organizations and takes part in Irish film festivals.

Byrne rounds out the Pat Pack quite nicely with his prominence and long-standing successful career.

It’s about time these four Irish acting giants all got together in a film.

Can’t wait to the powerhouse Pat Packers bring a classic Irish novel to Hollywood!