In The Hangover, three friends wake up smashed and dumb in Las Vegas. In The Hangover Part II, the same three friends wake up smashed and dumb in Bangkok. Director Todd Phillips and writer Craig Mazin took heat for repeating their $467 million formula, but when Hangover II made $586 million, they seriously considered screwing the critics and mimicking the script for a third time—or more.

"'How can you do it again?' We're going to do it 12 times," Mazin threatens jokingly at Caesars Palace in Vegas, where he, Phillips, and the rest of The Hangover Part III cast have returned to the scene of the cash grab. Why not? The franchise is the rare comedy to make solid international loot abroad. A morning-after headache is universal, be it from soju, ouzo or chablis. "Everybody's had rough nights, everybody's made bad decisions," explains Phillips. "I had a rough night last night."

But there's a problem. Despite being the most profitable series Mazin or Phillips have had—make that, may ever have—in their careers (the first two Hangovers are the two highest-grossing R-rated comedies of all time, just above Beverly Hills Cop and Ted) both men are ready to stop with Hangover 3. "It needs to end," stresses Mazin.

Bradley Cooper, Zach Galifianakis, Ken Jeong and Ed Helms in 'The Hangover Part 3'

"There's probably five legitimate, different versions of the Hangover 3 as far as directions that it could have gone," says Phillips. Ultimately, he says, "it just felt natural that it should be Alan's story." The cynical reason is that Zach Galfianakis' Alan is far and away the Hangovers' star. Here at Caesars, the casino offers photos with a Galifianakis doppleganger, but guys who look like Ed Helms need not apply. But the second reason is that Alan is the only character with room to grow.

Ed Helms already had his arc in the first film, drunkenly dumping his domineering girlfriend for Heather Graham's dippy hooker, and then rounded off by marrying way, way up to then-28-year-old ex-sorority girl Jamie Chung in The Hangover II—a plot point more implausible than a smoking monkey.) "Ed is really the unsung hero of these movies," insists Phillips. "It's been said that comedy is not action, it's reaction, and Ed is the king of reaction." Squint closely at his face, and you can see the faint scars of his character's Mike Tyson tattoo, which took an extra hour in the make-up chair every day. And Bradley Cooper's Phil is a consistent, content alpha ("I think his comedy comes in that attitude of, 'He killed a giraffe, who gives a fuck? Big deal,'" says Phillips).

As for Justin Bartha, the series has never cared about him and doesn't intend to start now. "Everybody's like, 'Do you hate Justin Bartha?'" defends Phillips. "I've been friends with Justin Bartha longer than any of these guys—he used to live in my house.'" Not that Bartha is complaining. "I make a lot of money on these for doing next to nothing," he jokes.

Ed Helms, Bradley Cooper and Zach Galifianakis in 'The Hangover Part III'

The Hangover III starts with Zach Galifianakis' Alan going off his meds and beheading a giraffe. ("I was in the shower and I was thinking of a horrible way to start this movie to just say, 'Here we go, grab on,'" says Phillips.) Within 15 minutes, his future looks so dark that the Wolf Pack agrees to drive him to a mental institution. "Filmmakers in their very nature are dark people," says Phillips. "If you're going to be tackling Alan's story, it's definitely going to be a little bit more emotional, because he's naturally more genuinely f--ked up." However, what's striking is that though Galifianakis descends from a line of funny, fat men who storm comedies just to screw things up—think Belushi, Candy, Farley—The Hangover III is the first to stop, take a serious look at his character, and realize he's simply not fit for society.

"Belushi was this kind of guy," explains Mazin, "but there was never one of those movies where all the characters in the movie said, 'Whoa, whoa, whoa, whoa. Listen, even though he's hysterical here at the frat house, we need to get him some help because he's dangerous.'" While the actual plot of The Hangover III is the guys' quest to wrest escaped con Chang (Ken Jeong) to a vengeful Vegas overlord (John Goodman), the real question is: what happens when the hijinks end and the Wolfpack is committed to being Alan's caretakers?

If that doesn't sound funny, it's because it sometimes isn't. The Hangover franchise has always has serious pretensions—just look at its art house cinematography by Lawrence Sher (Garden State). For better and worse, The Hangover III is as much a mix of drama, comedy, and a dash of weird romance as Silver Linings Playbook, which is why it makes sense that Bradley Cooper is the first to champion its sentimental turn. "There is no more inebriated devastation," says Cooper. "It's really: Let's take care of our friend."

The Hangover Part III 3 (Reviews) starring Bradley Cooper, Ed Helms, Zach Galifianakis, Ken Jeong and John Goodman

To ratchet up the stakes, Phillips has spent the promotional tour promising that at least one character will die. (It's actually more.) We won't say who—Phillips isn't quite as secretive as J.J. Abrams, but he's close—but we can say who wanted to die: Galfianakis. "I volunteered," he admits. As for his character's emotional reunion with toddler Carlos—played by the same child as the baby on The Hangover poster—Galfianakis groans, "We know this is a cheesy moment, but some people might like it—just bear with us."

Honestly, the whole group seems a little exhausted by the end of their whirlwind trilogy. At the press day in Vegas, most of the cast seemed a little sober and self-serious (which could also be the early Sin City wake-up call). They copped to having an almost anti-climatic wrap party on the final day of shooting: just a small gathering on the set with Galifianakis' Greek moonshine.

It's almost hard to remember that in 2009, Cooper, Helms, Galfianakis were big screen unknowns—such cheap risks that no one thought to sign the gang to sequel contracts. And lucky for them: while each made only $300,000 on the first film, they had the leverage to demand $15 million for the third. Everyone's already looking ahead to their future projects. Cooper is reteaming with Silver Linings director David O. Russell for American Hustle, Helms is taking on the Chevy Chase role in next year's National Lampoon's reboot, and Galifianakis is shifting into dramas with Birdman, the latest from Mexican auteur Alejandro González Iñárritu (Babel, Amores Perros). But if this is the Wolfpack's last vacation in Vegas—the town they put back on the map—they at least seem to be enjoying it for what it is. "I walked out and played The Hangover slot machine and won $200," beams Helms. Deadpans Galifianakis, "Life is really coming together for you."

Should part three really be the end of The Hangover franchise for good after its opening weekend haul only earned half as much as Part II? Read our review of The Hangover Part III.

The Hangover Part III is now playing in theaters.