"The Walking Dead" is the kind of show every network wishes it could have.

AMC's zombie smash is the No. 1 series on all TV in the key demographic of viewers ages 18 to 49, according to Nielsen. And with Sunday's Season 4 premiere, it stole the thunder from broadcast networks as they continued trying to build traction for new fall shows, including NBC's crime drama "Blacklist" and ABC's "Marvel's Agents of S.H.I.E.L.D."

Sunday's "Walking Dead" delivered 16.1 million total viewers. Only NBC's Cowboys-Redskins game on Sunday, plus CBS' smash hits "NCIS" and "The Big Bang Theory," drew more viewers.

PHOTOS: Behind the scenes of 'The Walking Dead'

Even more remarkable is the AMC drama's strength among the young adults that networks spend millions of dollars chasing. The Sunday night numbers for "Walking Dead" even outdrew what "Big Bang Theory" did during premiere week last month - and that was if you threw in all the viewers who watched the CBS comedy up to a week later on a DVR.

"NCIS" may have had more total viewers, in other words -- but they were a lot older than those for "Walking Dead."

Of course, AMC has far fewer original series than the broadcasters do. That means it can maximize exposure for one show at a time -- which is exactly what the network did with a "Walking Dead" marathon that preceded the season premiere.

But the fact remains that "Walking Dead" is a huge hit because a lot of people want to see it. Which would be a useful truth for the networks to ponder as they seek their own "Walking Deads."

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