The world's largest gathering of comic book fans is taking place in California. But organizers of the annual Comic-Con say this convention is not just for comic book fans. Hollywood, TV Networks and videogame makers are all getting into the game - helping to fuel the growing consumer appetite for costumed heroes and fantasy.

Everyone loves a costume party.

And when it's the world's biggest comic book convention - some find it simply too hard to resist dressing up. "Since I was 14, I have liked comics, so of course by default, we started going to Comic Cons when he was young.  He kind of grew out on his own.  It was his idea to dress up," says Jon Graham.

For serious action fans, this convention is as close as some will get to meeting their real-life super heroes - or just acting like one. "Everybody wants to see their comic book hero put into film and flying and [being tough]," says Geri Sumabom. "Doing all the things that we read about. We want to see that come to life.  It's great!"

Comic-con marketing director David Glanzer says the once-fledgling event has grown in recent years, thanks in part to Hollywood's love affair with action heroes. "This is our 41st year.  Each year is different.  Whether it be comic book publishers, toy manufacturers, or whatever.  Everybody's working on new projects.  And Comic-Con is the place you can see those projects before anybody else," he says.

The convention has turned into a marketing bonanza with celebrity guests this year including mega stars Brad Pitt and Angelina Jolie.

But regular convention goers complain the event has become too big. Milan Chakroboty says "I certainly do think that it has become a victim of itself in many ways, like getting into some of the events are almost impossible.  You have to get there hours and hours in advance."

But some say the convergence of popular culture into one giant venue is not such a bad thing. "You know it's great that Comic-Con has grown into this pop culture event.  This is the event!  In fact I was reading in Vanity Fair and they quoted that Comic-Con is the new Sundance, it is the new Cannes Film Festival," says J.J. Carwell

In recent years, Comic-Con has helped launch films such as Iron Man and Avatar to tremendous box office success.  This year, the number of new films being promoted has nearly doubled.

More surprised than most by the event's success is Stan Lee - the 87-year old co-creator of Spiderman and Iron Man comic books.  Lee is mobbed everywhere he goes. "I feel like a rock star in a way.  But the only bad thing about it - I don't get a chance to really enjoy the Con.   Because I can't just walk around and look at the exhibits," he says.

About 125,000 fans of comic books, movies and video games are expected to attend the 4-day event which runs through July 25.