By Gregory Ellwood
Special to MSN Movies

125,000 people. That's the estimate Comic-Con International provides as the attendance for last year's massive four-day convention in San Diego. That's more people than the largest college football or NASCAR stadium can hold. Long portrayed as "geek chic" by the mainstream media, Comic-Con has more than evolved. It's exploded and it's gone mainstream. Big-time.

During the past decade, the nonprofit convention has grown from its comic-book origins into a pop-culture happening with as much importance to the movie and TV industries as prestigious American events such as the Sundance or Toronto film festivals. Yes, science-fiction, fantasy and action flicks drive the entire show, but when the summer's top movies are "Iron Man," "Indiana Jones and the Kingdom of the Crystal Skull," "WALL-E" and "The Incredible Hulk" -- all films presented at last year's gathering -- we're talking entertainment fueled by Middle America. The convention has moved past its perception as a stereotypical gathering of sci-fi fans who live in their parents' basements (not that there is anything wrong with that) -- and both movie studios and TV networks have noticed. The festival was the launching pad for publicity campaigns for all four of the previously mentioned blockbusters and created major buzz for recent hits such as "The Chronicles of Narnia: The Lion, the Witch and the Wardrobe," "300" and "Sin City," just to name a few.

Most important to these previews is, of course, the fans, who are a huge differentiator for Comic-Con compared with other genre events. The Con takes over the entire San Diego Convention Center. Its massive Hall H seats 6,500 people and is constantly packed and has lines stretching around the building with people trying to get in for a chance to ask questions of their favorite stars. And to the fans standing in the hot sun to get into the hall, it's well worth the wait. Want a taste of some of the big names who have rocked the hall during the past few years? How about Angelina Jolie, Clive Owen, Edward Norton, Eva Mendes, Jessica Alba, Robert Downey Jr., Jennifer Love Hewitt, Andre Benjamin, Andy Samberg, Gwyneth Paltrow, Jude Law, Liv Tyler, Milla Jovovich, Rosario Dawson, Steve Carell, Anne Hathaway, Tobey Maguire, Kirsten Dunst, Topher Grace, Kate Beckinsale, Arnold Schwarzenegger (pre-governor), Jack Black (performing a mini-concert with Tenacious D, no less), Jamie Foxx, Jessica Alba, Natalie Portman, Nicolas Cage, Samuel L. Jackson, Hilary Swank, Jason Statham, Scarlett Johansson, Dwayne Johnson, Gerard Butler, Elijah Wood, Charlize Theron, Hugh Jackman, Michael Cera and Seth Rogen? And that's just the talent from the film industry. The presence of small-screen stars has been growing by leaps and bounds since Joss Whedon first brought the stars of "Buffy the Vampire Slayer" to the Con in 1998. Last year found the entire cast of "Heroes" attending with 5,000 people trying to cram into an already packed smaller hall (organizers are wisely moving them to the bigger Hall H this year).

According to David Glanzer, director of marketing and public relations for Comic-Con International who has an almost 25-year history with the event, the Con's relationship with Hollywood goes back to 1970, when the event was first held.

"It's easy to look at Comic-Con in the eyes of 2008 where we've seen guests like Ben Affleck or Angelina Jolie, but we're the same people, for the most part, who were here at the beginning," Glazner says. "So, for us, Frank Capra [attending] or Lucasfilm taking a booth to promote 'Star Wars' in 1976, that was a huge thing for us."

But according to longtime studio consultant Jeff Walker, the industry's love affair with the conveniently situated event south of Los Angeles didn't begin until the simultaneous release of the "Lord of the Rings," "Harry Potter" and "X-Men" series during the last decade -- properties with genre origins but of interest to wider audiences.

"After the last 10 years, more filmmakers, directors and actors are coming down and participating," Walker says. "A lot of them are fans that came of age and made films and wanted to share them with fans they grew up with. And that's particularly true of people like Bryan Singer and Peter Jackson. These are all fans themselves."

And as fans, they understand the enthusiasm of previewing material of an anticipated movie for the first time or making casting announcements in front of a captive audience. It's probably an exaggeration to say the studios have it down to an exact science, but they rarely misjudge the appetite of the fans. Paramount, in particular, had a smashing lineup last year with buzzworthy first footage of "Iron Man" and a "live" cutaway to the set of "Indiana Jones" where Steven Spielberg, Harrison Ford and Shia LaBeouf, the latter only weeks after the success of "Transformers," chatted with the spectators.

That day was also a keen reminder of how much the festival has changed. As many press members noticed, the hall was filled with families, a growing segment of the convention.

"We went out and looked at the line to come into that room and you would have seen probably 30 to 40 percent under 15," Walker recalls. "There were families with kids in strollers. There were young teenagers and preteens in line there."

Glazner adds, "When someone makes a disparaging joke about Comic-Con attendees, it's a lot less funny than it used to be, because our attendees are a very diverse group of people."

The convergence of Hollywood's marketing machine and the broadening of the convention attendees may hit a tipping point this year. The expected influx of Hollywood talent is why this year's four packed days have been the subject of rumor and conjecture for months and should lead to the convention's most star-packed lineup ever. Here's a quick run down of who is tentatively scheduled to appear ... the key word is "tentatively," because Comic-Con loves to keep the element of surprise intact:

"Twilight": The stars of the latest Internet and literary phenomenon, Kristen Stewart and Robert Pattinson, greet their fans.

"Max Payne": Mark Wahlberg makes his first Comic-Con appearance to promote the upcoming adaptation of the popular video game.

"RocknRolla": Gerard Butler, Jeremy Piven, Chris "Ludacris" Bridges and director Guy Ritchie -- can anyone say "boys' club"?

"Race to Witch Mountain": Dwayne Johnson knows how to work the con crowd like no one else. You can also guarantee a fan will ask him, "When are you returning to the WWE?" for the millionth time (the answer is "no time soon").

"X-Men Origins: Wolverine": Hugh Jackman is back as everyone's favorite self-healing mutant.

"The Mummy: Tomb of the Dragon Emperor": The popular franchise returns with Brendan Fraser and Maria Bello stepping in for Rachel Weisz.

"The Day the Earth Stood Still": Keanu Reeves and Jennifer Connelly are scheduled to chat about their remake of the '50s sci-fi classic.

"Death Race": Jason Statham, action-star extraordinaire, pitches this late-summer thriller.

"Push": Dakota Fanning and Chris Evans promote next spring's sci-fi thriller. And yes, that's not a misprint. Dakota Fanning will be taking fan questions!

"Pineapple Express": Seth Rogen returns to the convention floor after last year's hilarious "Superbad" panel to pitch his latest (and greatest) comedy with co-star James Franco and the rest of the cast.

"Watchmen": Zack Snyder brings his cast down for next March's highly anticipated adaptation of the legendary comic series. Patrick Wilson, Javkir Earle Haley, Matthew Goode, Billy Crudup, Carla Gugino, Malin Akerman and Jeffrey Dean Morgan are scheduled to appear.

"Terminator Salvation: The Future Begins": He keeps denying it, but Christian Bale is set to appear with co-stars Sam Worthington (Hollywood's next "it" leading man), Bryce Dallas Howard, Anton Yelchin and director McG.

"Star Wars: The Clone Wars": George Lucas and the voice of C-3PO, Anthony Daniels, will discuss the franchise's first animated cinematic endeavor.

Also this year, the TV contingent will come close to eclipsing its big-screen brothers. As previously teased, for the first time ever, the casts of "Lost" and "Heroes" are scheduled to greet fans in the massive Hall H, a venue previously only reserved for movies. And proof that the convention is continuing to evolve beyond genre, Rainn Wilson is scheduled to moderate a panel on "The Office" (no word whether Steve Carell will also attend) and the casts of "24," "Prison Break," "Bones" and the comedy "The Big Bang Theory" will also have panels.

New shows looking for love are J.J. Abrams and Whedon's latest, "Fringe" and "Dollhouse," respectively. "Knight Rider" and "Life on Mars" are also set. Returning favorites include "Ghost Whisperer," "Battlestar Galactica," "Chuck," "Pushing Daisies," "Terminator: The Sarah Connor Chronicles" and "Kyle XY."

And, as always, the fest never continues to surprise. Snoop Dogg and Paris Hilton have "graced" the convention with their presence in the past, and this year Tori Amos -- yes, that Tori Amos -- will appear to promote her new anthology book "Comic Book Tattoo." So, to recap: The convention will have Amos, Dakota Fanning and Ludacris all in attendance. Clearly, July's biggest party will be in San Diego.

Stay tuned, true believers. MSN Movies, MSN TV and MSN Video are teaming with Xbox this year to invade Comic-Con. We will provide daily updates, blogs and videos from the convention beginning Wednesday, July 24.

Are you interested in Comic-Con? What film or TV show excites you the most? Write us at heymsn@microsoft.com