The film is about a group of friends - Bradley Cooper, Justin Bartha, Zach Galifianakis and Ed Helms – who go to Caesars Palace in Las Vegas for Justin’s bachelor party and everything goes wrong. It ends up the group parties too hard, and when they wake up the next morning, they can't remember a thing. Their posh hotel suite is trashed and the groom is nowhere to be found. With no clue of what happened and little time to spare, the trio attempt to retrace their bad decisions from the night before in order to figure out where things went wrong and hopefully get Justin back to L.A. in time for his wedding. However, the more they begin to uncover, the more they realize just how much trouble they're really in.

And if you’re thinking this is going to be some stale and safe Vegas movie, it’s rated R, and I’ve heard from friends that have seen it that it’s great.

Anyhow, last year when they were filming in Vegas, I was invited – along with a few other online journalists – to the set of “The Hangover” to watch some filming and interview the cast. If you missed my set report you can read it here.

So while we were there we got to speak with the cast and the interview below is with Zack Galifianakis

During our interview Zack told us some extremely funny stories about filming in Vegas and he had us laughing a lot. It’s one of those interviews I really suggest listening to. If you’d like to hear the audio, click here. Otherwise the transcript is below.

“The Hangover” opens June 5^th at theaters everywhere.

Note: Zack walked in from filming a sequence where he was wearing a baby holder. It’s in the trailer. We had just watched them film the scene and everyone kept laughing…..

Question: What was cracking you up out there? Was the baby doing something?

Zack Galifianakis: Well, Ed was laughing and when someone laughs it makes me laugh. Just the reveal of the baby was making Ed laugh. He's just stupid. He just got giggly and I got giggly. That's what we were laughing at. And then it just got funnier because Todd, the director, got upset at us. And when someone gets upset at you laughing, it only makes it worse. It makes it so much funnier. So he was getting angry which reminded me of my father in church when I would laugh. Then my father getting mad only made it better. So that's why we were giggling. There's a baby doll that's a stand-in who looks like a real baby and the other day I was acting like the baby was masturbating himself and Todd goes, "Oh, we've got to put that in the movie!" So Todd had to ask the parents, "Do you mind if a grown man is acting like he's jerking off your baby?"

And the parents were fine with it?

Zack: I wasn't there for that. I would be too embarrassed. If they had said no, I would have been too embarrassed. There's no way I could have watched that. But people pimp their babies out.

Is it a rule that you have to show up hung over to the set every day?

Zack: Do I look hung over? I went out last night. I shouldn't have done it.  I got in at four. We went to a nightclub. I shouldn't have gone. But yeah. Today I'm playing the part for sure. I'm aching. It's just research. Just research.

I hear you got to go swimming in the fountain.

Zack: Yeah, I went swimming in the Caesar’s fountain. For the movie. I wasn't doing it on my own. It was tempting to get in that thing. It was nice. I went freestyle around and I haven't swam in a fountain in a couple of weeks so it was nice. Really nice.

Can you tell us a little about your character?

Zack: The guy's name is Alan and he's a guy who went to raves ten years ago and was probably affected by some of the substances he took at raves and he's still wearing the same clothes he wore at raves but he's gained like 25 pounds. He just hasn't bought anything new. That's basically the character. He's really kind of misplaced. He's hanging out with these guys but they really don't want him around because he's a weirdo.

Are you having fun playing around with the R-rating?

Zack: Yeah, they wanted it to be G until I jerked a baby off. It was going to be a Pixar film... But this has a lot more elements to it than just cursing for the sake of being R. I think it's a little bit more clever than that. I mean, it's dirty. There's some dirty parts in it. There's male nudity!

Were you given that characterization or did you come up with it on your own?

Zack: I came up with it when I was trying to figure out the wardrobe. I just told them I wanted tight clothes as if he had not bought. I also came up with that he runs a fan site for the Pet Shop Boys. Either that or the Jonas Brothers. We're not sure which one we're going to use. So he's just this older guy that's kind of creepy. It's a bit autobiographical I think. But you just start putting pieces together and imagining what he was and then, with that memory, you just kind of act with what you've given that character as history. I think that's the best way to try and do it.

So is the baby in a lot of the film?

Zack: The baby's in several scenes. I think there's four sets of twins that they just keep rotating. Three or four. I think there's four rotating in and out.

Can you tell the difference?

Zack: Yeah. That was Grant. And Grant has a sister named Avery. Then there's Mikala. I can't remember right now. I've only worked with four or five of them. Grant was the best. That baby hardly talked. That was a great baby. I love kids. I love babies. I love them. But not when you're hung over.

How much opportunity do you have to include your own comedy?

Zack: Well Todd lets you -- I mean, any actor can go vomit lines out -- but coming from a comic background, he lets you do whatever. You can just make stuff up. We do the script and then he lets us kind of play around, you know? A lot of breathing room which is really, really nice. Really, really gracious of him.

We heard improvising at the start of the scene. Does that stay or does that just help you get in the mood?

Zack: Well, we do it and then Todd can cut around it. He just lets us do it and then he cuts around it if he wants to. Like the conversation beforehand, it's not in the script. We were just playing around. He can cut into that. He might not use it. I don't know. I might be cut out of the whole film.

What are the pros and cons of shooting in Vegas?

Zack: The pros are that you can get prostitutes at the food court. That's also a con. No, the pros are that there is this energy that's just constant and, actually, shooting in the casinos is great because they pump so much oxygen in here and I really do think that that's kind of keeping me going. I haven't really slept but you just go off the energy of the casinos and the life here. And the big con is that there's very, very little sleep because of that energy. I just can't get any rest.

How do you know when the improvisation works and when it doesn’t'?

Zack: Well, as long as you're doing improvisation within the realm of the character, you can't just do it for the sake of the joke. I've done it a couple of times where, after, I realized that my character would never say it so I'll give it to one of the other characters and vice versa. "You should say that." If it doesn't feel right in improvisation, Todd will come up and say, "That's something you wouldn't say," and I'll agree with it. You just kind of keep that in check. You can't just do it for the sake of a joke. It has to be right. It has to fit the character, I think.

Did you Ed and Bradley have a lot of time to get to know each other before shooting started?

Zack: I knew both Ed and Bradley before this. Ed and I actually did a house swap and then Bradley I've just known. We haven't really rehearsed, but we have gone to many dinners where we'll talk about stuff. You just kind of jump into these things. There's not a lot of rehearsal involved in anything I've worked on. You just kind of go into it. But we do hang out constantly and it's very, very helpful. We'll go out at night and drink and eat. Or, those guys eat and they watch me drink.  All that process really helps. It was really a quick gelling on this set. There's a good vibe right away, I think. They probably don't think so.

What's your criteria for choosing to take on a certain film?

Zack: The money? (Laughs) I don't know. I just sort of take what comes up. I wish I could sit back and say, "Oh, I'm gonna wait for a Merchant- Ivory film to come my way. Or Ivory-Merchant. Whatever it's called.  But you just take what's given and then, hopefully, down the road you can be more choosy and only do, say, Wayans brothers movies. (laughs). That's my goal: to be more Merchant-Ivory-Wayans.

You're also doing some indie films, though. You've got "Visioneers" coming out. What's the status on that?

Zack: It's playing the festivals, but I don't know. Maybe someone will pick it up. It's a very odd little movie, but I like it a lot. It's really good. But on that movie I asked the PAs how much they were getting paid and they were getting paid more a day than I was.

Are your scenes with Justin Bartha all flashbacks or how does that work out?

Zack: I have a number of scenes with Justin, yeah. But the whole movie, chronologically, I don't think you would call it flashbacks. We drive to Vegas together, but I guess some of it is rewinding and trying to figure that stuff out. There is that. Absolutely. But we all have scenes with Justin.

Of the four of you, who's the party guy and who's the quiet one? What are the different personality types? What kind of instrument do you play in "Rock Band"?

Zack: The recorder. You know, I don't think anybody is wild and crazy. Bradley doesn't drink. (pretends to snore). Ed just talks about "The Office" all the time. No, I mean they're all gentleman. I guess maybe I'm the crazy one because I drink in my bathtub in my room and then call the front desk and ask them to remove the bible. But yeah. We go to dinner. We sit down and drink wine and talk politics. Even though last night, I did go out.

Did you go to the Mariah Carey birthday?

Zack: (Laughs) It was Nick Cannon. He's one of my best friends (laughs). It was so weird. He had all these people there that clearly didn't know him. It's so odd. And I didn't even realize that they're married. But yeah. I went to that. Shamefully.

Did you actually go up and wish him a happy birthday?

Zack: No. I was just staring at people. I don't know how to behave in those clubs. It's just fun to watch the cheesiest people in the world. But there was free vodka, so...

Did you wear any of your rave costume?

Zack: No, no. I was in a Brooks Brothers shirt. No rave clothes. Though that would be funny to go out in character. I did that once. I played a doctor on this TV show. I didn't know any of the other actors, but I had to wear doctor garb. They went out to eat and they didn't invite me so I kept my costume on and hung out at the bar where I knew they were eating. I wanted them to think, "What a fucking nerd. He's dressing up so that he hopes he gets recognized from the show." And nobody liked it. Nobody laughed. They all thought I was weird. It was so embarrassing.

At this point, are you more interested in doing stand-up or acting?

Zack: I don't know. I just kind of go with it. I get burned out on standup. But I like acting. I do like it. But sometimes you just feel like a monkey. You just feel like a complete tool. But I like it. I do like it. Stand-up is just more free. A lot more freedom because you just do what you want to do.

A lot of comedians are getting noticed by doing short films on the internet. Do you see that as something that's going to be the wave of the future?

Zack: Certainly, yeah. You don't have to go pay your dues as much, I think, as on stage. But if you have that background, it's helpful. It's always helpful to have that background. You can just throw something on and sometimes it sticks. People get TV deals by doing something in their grandmother's basement. It is definitely the wave. Everybody is trying to do all that stuff. I mean, the internet is the only reason that I've gotten work is because I've somehow created a line and people have seen it. And then I've been asked to auditions. So yeah, for sure. Absolutely.