Tens of thousands of people will hit downtown Denver for Comic Con Friday - it's the annual convention showcasing comics, TV and everything in between.

Many are there just to get a picture and autograph from their favorite stars - from John Cusack to Catherine Tate - they told 9NEWS why that's such a key piece of the culture of comics.

For one Con-goer downtown, it was Weird Al. For another, it's Nathan Fillion of Castle and Firefly fame.

But for Charles Rozanski, owner and founder of Mile High Comics?

"There's no one left that I would want to meet, to be quite honest with you," he tells 9NEWS.

He's been in the biz longer than most fans have been alive.

"I decided when I was 14 that I wanted to do this for the rest of my life," he says. "From the very beginning of comic conventions, going all the way back to like 1964 - it's always been a function of fans wanting to meet the people who actually create."

He says that's a 'why' that seems to supersede that of other genres and interests.

"If you go to a comic book writer and say, 'hey, I've got a plot twist you may not have thought of,' they're all ears," Rozanski says. "And that's the difference - comics, and to some extent film, are very collaborative."

It's why the $40 autograph doesn't sound so bad.

But how does Comic Con attract these big-name guests? Its organizers wouldn't tell us - they said it's a "secret sauce" they use that includes certain guarantees - many of them monetary.

But then again some don't charge to get their autographs.