Zac Efron has come a long way since playing teenage heartthrob Troy Bolton in High School Musical.

Come October, Zac Efron will be celebrating his 27th birthday, making it eight years (and 14 other film projects) since his debut in High School Musical.

In that time, Efron has become far removed from the persona we first encountered in the hit Disney musical, which brought him fame and fortune.

His image took a turn when he entered rehab for alcohol and drug addiction late last year; and just last month he was involved in a tussle with a homeless man, resulting in the actor getting hit in the face.

A recent cover story in The Hollywood Reporter reveals that Efron is keen to concentrate on his career by working hard and leading a more “low-key” lifestyle; he’ll just keep the bad boy image for the big-screen.

This is exactly what he does in his latest film, Bad Neighbours. In it he plays Teddy Sanders, a college student, who together with his frat brothers move into a quiet neighbourhood and starts all kinds of trouble, especially for his next-door neighbour Mac and Kelly Radner (Seth Rogen and Rose Byrne).

In an interview transcript provided by United International Pictures, Efron talks about the role.

What made you want to do this film?

Seth Rogen and (director) Nicholas Stoller got in touch with me about the project, and I immediately said yes. It’s a dream come true. If I had a fear, it was that Teddy would be a one-dimensional character.

There was a potential for the portrayal of fraternity guys to be that way since they’ve got a bad reputation, especially with parents. They, of course, do pretty bad things like partying hard, but at the core, the fraternity is built on a brotherhood, a bond.

It’s a system of breaking you down to build you up and taking you out of being so self-centred and worrying about yourself and caring for the group as a whole. You learn to work together and everyone helps each other.

Teddy is sort of a leader in that way. I wasn’t involved in a fraternity, but I know guys who were. While they’ve all been as crazy as Teddy in some ways, they’re also great guys. They’d take a bullet for you.

The moments that I am really grateful for in the film were the ones where we were able to show Teddy’s humanity because he does care about his brothers.

Were those party scenes in the film fun to shoot?

On set, everything was very professional. We would utilise every single element of the party. As soon as we cut, it was down to business with me working on the character and Seth producing. There was a lot to get done and a lot of moving parts, so it was strange. It was a really exciting party that was very tense!

It seems that improvisation played a big part in the film. How much input did you get when shooting a scene, such as the one where Teddy and Pete (Dave Franco) riff off about “bros before hoes?”

Some of the lines were strung together for that particular scene in the film. I don’t think we got all of them consecutively like that, but most of that scene was straight improvisation. Some of it didn’t even make sense.

We were literally trying to come up with them on the fly. If I ever started to struggle, Dave would whisper something to me and I’d finish it and vice versa.

Then, out of nowhere, Nick or Seth would yell one line from off camera and we’d start laughing.

There’s no ego; if you’re given something great, you take it.

You get to fight Seth Rogen in the movie, what was that like?

It really was fun to shoot that fight scene. I was looking forward to it. Since we shot that towards the end of the movie, I think we were ready for it. It was all comedic fighting and never that serious. There were some fun stunts as well.

Was it easy finding a rhythm with Seth Rogen?

It was natural working with Seth. I really liked that the relationship evolves because they could have been best friends in another life. I think they’re very similar in a lot of ways.

Teddy lives in fear that he’ll never really have what Mac has with his family and is looking at the peak of his life. Mac sees all the potential in the world in Teddy, so it’s a fun dynamic.

The buddy moments are fun, too. All of the scenes where we’re happy together were improvised. We just sat on a couch and talked about things.

What was the most challenging thing to shoot?

Some of the fight scenes with Dave Franco were really difficult. In one scene, it was just supposed to be a simple punch, but when I connected with the wall, I got a boxer’s fracture in my hand.

It was the first take, so we still had several hours of shooting to get through. If anyone had found out about my hand, it would have stopped filming for the day, so I didn’t tell anybody. We kept filming even though I knew my hand was broken.

Nick was the first one to notice it and asked me if there was something wrong with my hand. By then, it was swollen like a grapefruit. I got surgery that night. That was a hard day!

> Bad Neighbours opens in cinemas today.