Brad Pitt
Brad Pitt Bang Showbiz

BRAD Pitt was in Sydney for the premiere of his latest movie World War Z on Sunday night, and admitted being the hero of a zombie apocalypse is nothing compared to looking after his family.

"The only thing that keeps me up at night is knowing is everyone safe. Are the kids safe, is mumma [Jolie] safe, is the house locked?", he tells

"It totally informs the film", he added, referring to his role as family man and ex-U.N . Investigator Gerry Lane, who faces the epic task of trying to find the source of the zombie outbreak.

But what's easier for the 49-year-old dad - battling zombies or raising six kids? "Zombies. Zombies any day", Pitt tells reporters, flashing that smile.

"Although, you can survive six kids and our film is pretty rough, so..."

The 49-year-old actor surprised fans at another screening of 'World War Z' on Friday night in Los Angeles in the US, leading to speculation that he might do the same thing for the Brisbane screening.

Pitt, who has been on a worldwide promotional tour for the film, delighted fans by showing up unannounced at the screening, and addressing the audience before the movie began, according to

He said: "I've been on the's been amazing, but damn it's good to be home.

"Thanks for coming out. ('World War Z') is big, it's bold, it's badass. You've never seen anything like it.

"It's the most intense thing you'll see all summer. If not, we'll give you your money back. Let's get this party started."

The actor has made similar surprise appearances at cinemas in Chicago, Philadelphia, Atlanta, Georgia, and also showed up at a theatre in Austin, Texas, on Thursday (06.06.13).

World War Z hits cinemas on June 20.