Thousands of "superheroes" have gathered for the four-day Comic-Con International being held at the San Diego Convention Center. Comic-Con is the nation's largest celebration of comic books and pop culture.

The convention, which started Thursday, attracted Storm Troopers, Flash Gordon, Batmen, Spider-Men and even characters from toy makers. One photographer was seen wearing a Wonder Woman costume.

Organizers of the event say these superheroes will be walking the streets and artists and animators will be treated like A-listers when fantasy will reign until Sunday.

Blair Butler, a comic-book expert who hosts a show on cable's G4 network said, "It's fondly referred to as nerd prom." Over 100,000 are expected to participate in the event.

Organizers said costumes are key to the event. Bree Bahnmiler, Kristen Perotti and Michelle Moody, all 19 told Yahoo News they have planned their costumes for this year's Comic-Con immediately after the 2005 convention ended.

Perotti, who is wearing an orange suit to look like a member of a Japanese band called Psycho Le Cemu at the opening adds, "This is, like, our life."

Bahnmiller was splattered with fake blood to look like Heather, a character from the horror video game, "Silent Hill 3." The trio said they have different costumes for each day of the convention. "It's like Halloween for four days."

Comic-Con spokesman David Glanzer, a 22-year veteran of the event said, "Our demographics show that people who come to this event see movies on opening weekend. Studios have an opportunity to talk to the people who buy those movie tickets or who tune in every night of the week to watch those shows and get feedback."