Seth Rogen developed a mean streak to make it in Hollywood.

The actor is renowned for being one of the nicest guys in the industry but he insists he had get a nasty side to succeed.

He revealed: ''Oh, I've had to motherf**k a few people every now and then. It's a relationship driven city (Los Angeles) in a lot of ways, and a relationship driven industry. If you're perceived as someone who's always happy, then you won't get treated as carefully as someone who might go ballistic every now and then.''

At the age of 18, Seth - now 31 - fired his business manager before clashing with movie mogul Harvey Weinstein over how 2008 comedy 'Zack and Miri Make a Porno' was marketed.

He told The Guardian newspaper: ''[Harvey is] a well-documented psychopath. He was using some of [Judd Apatow's] movies to sell that movie, which was specifically bad because it threatened one of my closest relationships, and I was working with Judd at the time.''

Although this might seem harsh, Judd revealed Seth is ''less needy'' than most people in Hollywood and brings his acting friends together with his various projects.

Judd added: ''Lots of us are loners. At the end of the day, we would rather be by ourselves. Seth likes being around people. He's much less needy than most of the people in the comedy business. He doesn't desperately seek approval.''