SAN DIEGO -- Pop culture and animation fans, many of them dressed as their favorite animated characters, lined up Thursday outside the San Diego Convention Center for the opening of the star-studded 39th annual Comic-Con International Convention.

"We have always been into the geek culture, you know, we are really into movies and such so we thought we would come this year," one couple dressed as "The Incredibles" told a local TV station.

The convention features celebrity appearances, hundreds of exhibits, seminars, art shows, gaming, autograph-signing sessions, film screenings and a masquerade party.

Keanu Reeves and Jennifer Connelly, who will discuss the upcoming movie "The Day The Earth Stood Still," are among the Hollywood stars slated to promote their films and television shows at the convention.

Actor Mark Wahlberg will join Mila Kunis from "That 70s Show" and rapper Ludacris to talk about turning the video game "Max Payne" into a movie.

Chris Evans, Dakota Fanning, Djimon Hounsou and Camilla Belle will give a first look at the science fiction film "Push."

Dan Aykroyd and Ernie Hudson will talk about "Ghostbusters: The Video Game," Emmy Award-winning animator Seth MacFarlane will take questions on his series "Family Guy" and "American Dad," and Kiefer Sutherland will talk about the return of television's "24."

There will also be appearances by Samuel L. Jackson, Jennifer Love Hewitt, "Knocked Up's" Judd Apatow, "The Simpsons" creator Matt Groening, musician Tori Amos, television's "Mythbusters" creators Jamie Hynemann and Adam Savage, and actors Kal Penn, John Cho and Neil Patrick Harris of "Harold & Kumar Escape from Guantanamo Bay."

Legendary science fiction author Ray Bradbury, who is 87 years old, is scheduled to be there, along with monster writer Forrest J. Ackerman, suspense novelist Dean Koontz and dozens of comic book writers and animators.

More than 125,000 people a day are expected to attend, which is about the same as last year, according to organizers.

The crowds lining up to get into the San Diego Convention Center have caused gridlock on Harbor Drive and in surrounding Gaslamp Quarter streets, according to police, who are urging motorists to take alternate routes and avoid the area.

The annual four-day convention, touted as the largest gathering of its kind, draws to San Diego thousands of animation, science fiction and pop-culture enthusiasts from around the country.

The convention runs through Sunday, but don't expect to get a ticket if you don't already have one.

Four-day passes and single-day tickets are both sold out, according to organizers. Four-day tickets are being sold by private individuals online for as much as $250.