Then came "The Hangover," which would go on to become the highest-grossing R-rated comedy in North American box-office history. A 2011 sequel would take in more than half-a-billion dollars worldwide. And next week comes the third and allegedly the last of the trilogy of films about friends on road trips gone extremely awry.
Folks still have trouble pronouncing Galifianakis but the careers - and lives - of all three co-stars have been changed forever by the series.
"I never would have gotten 'Hangover II' if it wasn't for 'Hangover I,'" joked Helms in a recent joint interview with his cast mates.
'"The effect it's had on my life, from a career standpoint, it just is off the charts. I've gotten to do some really great, cool, fun stuff that I never would have been able to do," Helms said.
Those include two well-reviewed 2011 low-budget comedies, "Cedar Rapids" and "Jeff Who Lives at Home."
Before "Hangover," Galifianakis was somebody - making a living as a stand-up comic, whose credits included his own Comedy Central Presents special. But that success was nothing compared to what would come. "Well, you know, financially," Galifianakis said, winding up for a Mother's Day joke. "It (was) really great to be able to pay to get her a salt-and-pepper shaker set."
Asked Cooper: "Set?"
Helms: "Salt AND pepper?"
Galifianakis: "For years it was just salt, just the salt shaker."
"Not even the shaker," added Cooper, "just the salt in a Ziploc (bag)."
"So now I can afford a set," Galifianakis continued, laughing. "So that's how it's changed my life."
Cooper's star was already on the rise before "Hangover," after having had done a number of TV series (including five seasons on "Alias" and starring in Fox's short-lived "Kitchen Confidential"). He acted opposite Julia Roberts and Paul Rudd on Broadway in "Three Days of Rain" (2005), and made a strong impression as a maid of honor's hotheaded boyfriend in the big-screen "Wedding Crashers" (2005). Then came roles in Jim Carrey's" Yes Man" (2008) and the ensemble rom-com, "He's Just Not That Into You" (2009).
In fact, Cooper was already such hot stuff, he'd hosted "Saturday Night Live" some four months before the first "Hangover'''s release.
And yet, Cooper said, the "Hangover" series also changed the course of his career.
"The truth is, 'The Hangover' sort of equally hit us all," he noted, pointing to film studio Relativity Media's giving him the lead in his first major big-screen drama, "Limitless" (2011), opposite Robert De Niro. "If I had not been a part of a movie that was financially lucrative, there's just no way," Cooper explained. "And then, following the success of 'Hangover II,' I don't think I could afford to do four movies where you just don't get paid that much."
Among them: "Silver Linings Playbook," for which he earned an Academy Award nomination as best actor.
"We've also just learned about ourselves," Cooper said. "We've all grown a lot. There was the movie and then what happened with the movie, and then being about to go all over the world. I had never done that before ... It's been a multi-faced learning experience."