Zac Efron teams up with Seth Rogen for the new R-rated raunchy comedy “Neighbors,” about a hard-partying fraternity that moves in next door to a young couple with a new baby.  Efron, 26, and his co-star Dave Franco sat down with FOX411 to talk about their fraternity knowledge and Efon’s past party days.

FOX411: What is your frat knowledge, what is your frat background? (Dave) you were in a fraternity?
Dave Franco: I was not, I was at USC though where there was a huge Greek system so I was around it plenty.
Zac Efron: Yeah and I'd say I was around it, you know, I went to several parties and stuff like that but what we needed to know for this movie we pooled our knowledge.
Franco: I think the main thing was we hung out a little bit before the movie just to make sure there was that natural chemistry and we had somewhat of a bro-mance so we wanted that to work.

FOX411: You’re a little older than [the characters you play.] Did you relate to the guys on the other side of the fence?
Efron: Any character Seth plays I always tend to agree with that character more. In this one he's like growing up and dealing with the responsibilities of having a family but still wanting to be young, and to go out, and have fun, so he's envious of the fraternity next door and I've felt that way for sure... I can relate to that feeling, but then, I've been in the other place. That's the thing, you've been, you've always been to where the fraternity is before so you kind of fall back to it.
Franco: Yeah there was a time and place for college, and I had a great, great time but I'm past that. I'm like, I'm a grandma now, I have two cats so I just want to stay in on the weekends. I'm happy to be in bed by 10:30.

FOX411: Zac you’ve been open about putting the party days behind you and so was the timing of this challenging at all? [Efron recently went to rehab.] Did it help at all?
Efron: I think it was perfect... it kind of put... it was the last nail on the cross you know? So to speak. But it was cool. I knew how to do it right, for the movie.

FOX411: I saw you have a very healthy routine now. Can you share a little bit about what you do?
Franco: We've been pounding our green drink all day (Efron picks up glass)
Efron: Yeah… this is like a vegetable drink

FOX411: is that your thing?
Efron: It's one of my things.
Franco: It’s a good thing to have.
Efron: I like to drink my vegetables.

FOX411: Flexing your comedy muscles… like to branch out into the raunchiness? We haven’t seen you do something like this really.
Efron: That was fun. I think I always waited for the right place to do it and I think this is the best place, with Seth… and all the guys in our fraternity Dave, Chris, Jerrod.
Franco: It's a very safe environment where these guys, they're not going to let you fail you know, there's so much improvisation which is scary but if you have an off day if you wake up and you're tired or you’re sick or whatever if you just can't figure something out that day you have five writers off camera yelling funny things for you to say and you can't fail it’s awesome.