Since 1970, it has evolved into a pop culture convention, and Hollywood has taken notice.
About 125,000 fans are expected to push through the doors of the convention, and the movie that gets their attention can be instant Internet chatter.
Only hours into the convention, and already they're talking about 'Twilight' movie, a vampire romance.
"This room was full of about 7,000 screaming. It was like a Beatles concert. They're using this place to spread the word," said Anne Thompson from Daily Variety.
The convention is all about marketing. It's the place to show off new and limited merchandise.
"These are the guys who will become the evangelists because they were able to see something early, tell all their friends about it, and that word-of-mouth, combined with the technologies that enable them to get the word out. It's a pretty powerful thing to be able to attend something like Comic-Con," said Lisa Gregorian from Warner Brothers.
Actor Robert Englund attended to talk about his new movie 'Jack Brooks: Monster Slayer'.
"I just think it's great that we are allowed a birth here at Comic-Con, and that Comic-Con has room, along with the big huge blockbusters and all the gossip and rumors about what's coming out, to also allow the smaller films that also serve the fans as well," he said.
The convention is also big business for a small movie like 'The Chosen One', coming soon to DVD.
"It's a lot of exposure. Everybody is coming to Comic-Con," said Chris Lacky from 'The Chosen One'. "It's sort of this hub of geek culture, and that's what my movie's all about."