FOR A franchise that's coming to an end, Bradley Cooper, Zach Galifianakis and Ed Helms appear to be in remarkably upbeat spirits.
The stars of The Hangover have developed a friendship which continues even when the cameras are switched off.
The Wolfpack's off-screen and on-screen chemistry, along with the celebrity cameos, undoubtedly helped The Hangover become a huge success around the world.
Todd Phillips's award-winning 2009 comedy about a wild stag party in Las Vegas transformed the trio into recognisable stars, spawned two sequels and propelled Cooper into the Hollywood A-list.
But Oscar nominee Cooper (38) insists: "The Hangover sort of equally hit us all. We've just learned about ourselves. We've all grown a lot."
Once again directed and co-written by Phillips, The Hangover III, which comes exactly two years after the 2011 Bangkok-set sequel, marks the final outing for the pack, who comprise teacher Phil Wenneck (Cooper), the unofficial leader; dentist Stu Price (Helms), the group's voice of reason, and their out-of-control friend Alan Garner (Galifianakis).
After their wild adventure in Thailand for Stu's wedding, Phil and Stu swap their uneventful married home lives for a road trip to Sin City, staging an intervention with Doug (Justin Bartha) to get Alan into rehab.
What seems like a straightforward journey turns into an epic expedition, with the return of deranged gangster Leslie Chow (Ken Jeong), the mysterious Marshall (John Goodman), fighting roosters and even a giraffe.
"This movie was rugged, brutal and massive. We have parachutes flying around Vegas at night, wild animals in places where they shouldn't be, lots of crazy things going on," explains Cooper. "But it's all grounded. I don't think there was ever a point where Todd or anyone thought, 'Let's outdo the first or second film'. The intention was just to tell a good story, and it feels like the normal progression of the lives of these three guys."
Galifianakis (43) says: "This time, we're really able to close the book, in a way that's congruent with what we built in the first movie. I think it needed a bit of closure and it's a nice storyline for the third film."
The third film sees bigger stunts, including Galifianakis and Cooper abseiling down a 60ft structure.
Galifianakis reveals: "I'm afraid of heights. We were dangling from a wire six or seven floors up. We had harnesses so it was completely safe, but my irrational mind told me otherwise."
Returning to Vegas – the film's unofficial star – was like reuniting with an old friend for the trio.
"I never came to Vegas before the Hangover movies. I was never drawn to it," admits Helms (39).
"But since I've been here so long working on these movies, I've really grown to love it. Going back could only be described as completely bananas because not only are we all more recognisable now, but The Hangover is such an institution there.
"It's hard to walk through the lobby or play blackjack without drawing a crowd or having fans come up to say hello... As long as I wear my Klingon make-up, no one will recognise me."
Yet he can recall a very Hangover-style story when he was mobbed by eight strippers.
"Zach and I walked through the lobby and it was the Spearmint Rhino's staff night out so there was a pack of beautiful ladies and they spotted us. I turned to Zach to say how do we handle this, and he was gone. So I took some pictures and gave some autographs – and got a few numbers," he recalls, adding: "Beautiful women hunt me down all the time."
It was a different story for Cooper, who even managed to attend an Elton John show with his mother Gloria.
"We're not rock stars. That's what is wonderful about the city – it's indifferent to anything other than what is going on here," he says.
"In the first one, we were in the elevator with tiger scratches on our neck and no one cared. It's not that different now. People might recognise us but they're not looking for us, they are looking to party."
Having played the characters for three films, saying farewell to their alter egos won't be easy.
"It's kind of bittersweet knowing that, after this, I won't be able to play Alan ever again. It was a nice run though," admits Galifianakis.
Helms's role in the US version of The Office is also ending, the finale aired on American screens last week.
"It's the right time but damn sad," he says. "Outside of my personal life, the two most colossal professional engagements of my life – The Hangover and The Office – are both ending. I am so grateful for both and am so excited for what's next."
Cooper, who is sporting 1970s-style curly hair for his new role in American Hustle, says: "I think we all know our characters more because we've lived in their skin for three movies. And in doing so, it reminds me of how much I'm not like Phil, rather than how much I am like him."
He's well aware that the franchise has been a life-changing opportunity.
"What's so great is all three of us doing this. So we really did go through this whole trilogy as a group."
While the trio won't be nursing any more Hangovers, there's a possibility they could reunite on screen. "I'd love to work with them again, but the franchise is done. The Hangover was a great experience of my life, and I'm lucky to be a part of it," says Cooper.
Read George Byrne's Review in the Entertainment section