Josh Brolin worried he might ''ruin'' the whole 'Men In Black' series by appearing in the third movie.

The 44-year-old actor plays Young Agent K in the film alongside Will Smith and Tommy Lee Jones - who reprised their roles in the sci-fi movie as Agent J and Agent K respectively - but he was concerned about how his co-stars might react to him joining the film franchise.

He said: ''I thought, 'Oh, yeah, this could be a career-killer. I could ruin an entire series, because I'm severing this great iconic duo, this great chemistry that people really enjoy'.

''If someone came to my franchise and said, 'Listen, you're still going to bookend it, but we're going to bring in this younger guy instead', I can't imagine I wouldn't be like, 'Huh? What are you talking about?' I don't know if he felt like that. And if he did he'd never tell me.''

Despite starring in a number of big blockbusters, Josh - who has been married to actress Diane Lane since 2004 - admits he no longer feels he has to ''push'' himself in life and doesn't mind taking the ''boring'' approach.

He added to The Times newspaper: ''I think when I was younger I felt the need to push, and keep pushing. Well, I don't feel that need any more. I think it's OK to be boring. ''