With 15.7 million viewers of its Season 4 finale in March, as well as 30.4 million Facebook fans and 2.7 million Twitter followers, AMC’s “The Walking Dead” is one of the most popular shows on television – and, as a result, it has a predictably passionate fan base.

These are fans eager for related content, but they have exacting standards. And that means the brand and its partners have both huge opportunity and responsibility.

According to Greg Braun, executive creative director of advertising agency Innocean, super fans are actually super marketers.

“It’s someone that is inherently not satisfied with being a witness, but wants to participate,” Braun said during a recent Advertising Week panel. “We as marketers have to give them opportunities. We can’t just interrupt – it has to be relevant…and the last thing is authenticity. If we’re not authentic to that property, they’ll tear a brand apart.”

To that end, Braun worked with Hyundai to create the Walking Dead Chop Shop, an effort that gives “Walking Dead” fans the opportunity to create their own zombie survival machine through an app and website. Fans start by choosing a Hyundai model – such as those featured in the show – and add armor, survival accessories, and designs from a range of options, including nearly 300 different car parts, according to a press release when the effort was announced in August. Fans are then able to share their creations, get survival scores and test the vehicles in scenarios inspired by the original “Walking Dead” comic books.

According to Braun, the key to building the campaign was looking for ways to empower fans, or what he calls “savvy listening,” noting, “It’s not always what you want to hear.”

Case in point: The Chop Shop, which started out as what Braun called a product placement and expanded to include a 1:1 scale zombie survival machine for Comic Con, was loved by general “Walking Dead” fans, but not hardcore fans.

“They were very specific – ‘There’s not enough ground clearance to get over skulls,’” Braun said. “Or they said, ‘The low profile tires are going to slip on the guts.’ We listened and regrouped and said, ‘If you can do better, let’s see it,’ and we gave them the tools to do that.”

Since then, the Chop Shop has since yielded 296,000 zombie survival machines.

But, Braun said, the brand and its agency partners continued to listen. Hyundai initially provided features like flame throwers, machine guns, and saw blades, but when those most passionate fans asked about smoke screens, the brand delivered, empowering those consumers with more crowdsourced parts.

“It’s about respecting the audience and listening,” Braun said. “The listening never stopped.”

Hyundai even sold a few of the machines as a result – although not, Braun noted, models with machine guns.

“We knew we had to be authentic,” Braun says. “We partnered with [‘Walking Dead’ creator] Robert Kirkman and his company, which is always very diligent about being authentic to this property.”