Once, amusement parks used barkers at the gates to lure crowds. Now Six Flags Theme Parks is trying a new way to draw them in: viral marketing.

Six Flags has enlisted a chic marketing agency, 42 Entertainment, to publicize two revamped thrill rides using not newspapers, radio or TV, but the Internet and social networking sites such as Twitter.

Six Flags is remodeling two major coasters: Medusa at Six Flags Great Adventure in Jackson, N.J., and Superman Ride of Steel at Six Flags New England. Both will open by the start of the summer season. Sophisticated additions such as on-board audio and corkscrew turns past flames and fog are being installed. Executives looked for an equally sophisticated way to market them.

For that, they turned to 42 Entertainment, which has specialized in alternative reality games (ARGs) for seven years, each year building on the social media du jour. The agency designed the 15-month campaign for last year's blockbuster flick The Dark Knight, waged via an interactive online game, YouTube videos, and real-world flash-mobs and "Gotham campaign rallies." Titled "Why So Serious?" it reached 10 million active players.

"We're trying to engage our guests in a deeper, more interactive way," said Angie Vieira Barocas, senior vice president of marketing at Six Flags.

ARGs are a complex form of viral marketing - a term deriving from the notion that the marketed idea should spread like a virus, from person to person, to create a buzz about the product.

Viral marketing has been around since the late 1990s. But the rising popularity of social networks such as Facebook and Twitter present new ways for potential fans to learn about the rides and network with other potentials.

According to Susan Bonds, president and chief executive officer of 42 Entertainment, Six Flags is the first amusement park to use an ARG for marketing. The campaign is a complex interactive virtual reality game with a Superman theme. It targets two fairly large and distinct groups: coaster enthusiasts and Superman fans.

The first step was to create an issue of The Daily Planet, the newspaper where Superman (as Clark Kent) and Lois Lane work, with stories relating to the coasters. It directs readers to online assets, such as blogs and the online game.

Next, distribute the "papers" at conventions of coaster and comics enthusiast, and as inserts in traditional media such as the Village Voice, Philadelphia Weekly, the Boston Phoenix, the Hartford Advocate, and the Valley Advocate.

An actor using the alias Jimmy Olsen (cub photographer for the Daily Planet) posts updates on his blog, Truth to Power, about Clawshun Industries, hired to build Six Flags' new coasters. As players discover, the company is a front for the evil Lex Luthor's LuthorCorp and his plan to brainwash all of the riders. Olsen appeals directly to players to help decipher clues in an effort to thwart Luthor. The blog links to Web sites that contain buried clues for players to decipher. If no one solves the puzzles, the game stalls.

It all leads to the "big reveal" of the two coasters sometime before the start of the summer season.

One of the major "rabbit holes," or ways users can be introduced to the game and start playing, is through Jimmy Olsen's Twitter page. Olsen has more than 1,000 followers of his Twitter updates - "tweets" - through which users learn of developments and can link to his blog.

"Twitter has been amazingly popular," Bonds said. "We're using that social tool just as it's blowing up."

Not halfway to the big reveal, and already, according to 42 Entertainment, 500,000 people have been exposed to the campaign, with 15 to 20 percent working collaboratively to solve clues and move the game forward.

The networking will not stop after the big reveal. Six Flags is one of a small number of companies now looking to hire a full-time, salaried social networker. This puts them a little ahead of the game in folding social technologies into standard business procedures, Vieira Barocas said. She says the position calls for someone with "a diversified skill set," not only the traditional skills of a media relations post, but also the ability to reach the target audiences via the Net by following blogs and actively engaging guests and potential guests, again through social networking sites.

In-house, Vieira Barocas says, this Webmaster is referred to as "the Twitter-Dude."

Contact staff writer Shannon Curley at 215-854-4193 or scurley@phillynews.com.