The Walking Dead's mid-season finale was this past Sunday. Without giving away any spoilers, I'll just say the episode was extra gory. AMC Networks' (AMCX -3.09%) zombie thriller is known for its ability to bring depth to a traditionally one-dimensional niche, but there's another, even more innovative practice at work here.

I'm alluding to Talking Dead, a live talk show that airs after the conclusion of each new episode of The Walking Dead. AMC rolled out the tandem series two years ago to modest reviews, and its audience has been growing ever since. Over 5 million viewers tuned in to see what host Chris Hardwick had to say about Dead's Season 4 premier earlier this year. This was more than Sunday mainstays like Fox's (FOX) Family Guy, NFL Countdown on Disney's (DIS -0.20%) ESPN, and Homeland on CBS' (PARA -1.03%) Showtime.

I'll repeat: A companion cable talk show is outdrawing actual comedies, dramas, and sports from the biggest networks on television. Let that sink in.

Courtesy AMC Networks.

So how is this possible? Three explanations.

The carryover effect

The obvious reason for Talking Dead's success is The Walking Dead itself. Halfway through its fourth season, the series continues to be TV's No. 1 show. On average, about one-third of its viewers stay glued to their TVs following the conclusion of each new episode. This carryover effect is partially possible because Talking Dead's airtime is 9 p.m. Eastern. The show doesn't have to go head-to-head with any heavyweights from earlier in the night.

AMC's decision to extend Talking Dead from 30 minutes to a full hour appears to be driven by ad revenue. In its latest quarterly earnings call, the company revealed advertising revenues are still growing by double-digit percentages year-over-year. Ad rates for both Dead shows have nearly doubled since last year, and The Walking Dead's average charge of $400,000 per 30-second spot dominates CBS's Big Bang Theory ($316K) and How I Met Your Mother ($166K), and Fox's Family Guy ($206K). According to Ad Age, it's second only to Comcast (CMCSA 1.65%) and NBC's Sunday Night Football.

Obviously, good timing isn't the only thing that makes Talking Dead so popular.

The show is geared toward fans

Another simple, yet important explanation for the show's success is its format. Rather than organize itself like a traditional talk show, Talking Dead is laid out as if The Walking Dead's most hardcore supporters have written it. In some sense, they have. Host Chris Hardwick is a self-proclaimed zombie super freak, calling the gig a "dream job," and it shows. Hardwick's interviews make it evident he's heavily involved in the fandom that surrounds The Walking Dead, and his Twitter account is a go-to spot for plot theories.

Within the hourly show itself, Hardwick features recurring segments designed to stimulate viewer interest, from call-in questions to interactive polls. The show's 'Dead Yourself' fans of the week is also a nice touch, and its 'In Memoriam' portion gives an essential recap of all deaths in the previous episode. 

Exclusive extras

That's not the only exclusive extra featured on Talking Dead, though. Hardwick also hosts a few actors from the series each week, in addition to periodic visits from producers and writers. This past episode, for example, featured a discussion with Scott Wilson and Lauren Cohan, who play Hershel and Maggie on the show itself. Series maestro Robert Kirkman, the creator of the original The Walking Dead graphic novels, was another guest and gave viewers a few key insights on what to expect in the future.

Courtesy Skybound.

A behind-the-scenes interview with Andrew Lincoln, the man responsible for the main protagonist Rick, capped the show.

AMC's willingness to give Hardwick the freedom to explore everything—aside from spoilers—is Talking Dead's true calling card. It's the reason such a high volume of viewers stay on the channel for another hour. If you fail to watch Talking Dead, you might miss a key plot point that's developing, or you may not understand the rationale behind a character's decision. Few networks have given fans such comprehensive access before, and none have done it on a week-to-week basis like AMC.

The zombies will never stop 

The network has already renewed The Walking Dead for a fifth season, and a companion series created by Kirkman himself is slated for a 2015 premier. AMC President Charlie Collier has called the direction a "no-brainer," and he's absolutely correct.

With more graphic novels on the horizon, this universe will continue to expand, furthering the need for a guide like Talking Dead to explain what it all means. Because of the talk show's success, I wouldn't be surprised if other TV networks adopt a similar model. At the very least, AMC's willingness to provide a Talking Bad with the final episodes of Breaking Bad indicates it's open to explore the format with other series.

The Walking Dead is the dominant name in the multi-billion dollar post-apocalyptic genre, and with tons of source material yet to be used, it's reasonable to expect the story to continue for the next decade at the very least. Robert Kirkman says he wants to "tell the zombie movie that never ends," so this prediction may end up being far too modest.