Despite its standing as arguably the most hyped show to hit the small screen this fall, the success of Disney's (NYSE:DIS) new Marvel-inspired Agents of S.H.I.E.L.D. certainly wasn't always a foregone conclusion.

Disney Stock, Agents of SHIELD
Image source: ABC

To be sure, though the series started off strong, drawing 11.9 million viewers and earning a 4.6 ratings share in the key 18-49 demographic for its debut, it raised eyebrows across the industry last week after fewer than 8.7 million people tuned in to the second episode, for which ratings dropped by almost a third to 3.3.

Meanwhile, both NBC's The Voice and CBS' (NASDAQ:VIAC) hit drama NCIS held up substantially better and continued to dominate during their second week on both metrics, grabbing ratings shares in the 18-49 demographic of 4.5 and 3.5, respectively. After that, many were left wondering whether the novelty of third-place Agents of S.H.I.E.L.D. had simply worn off.

After all, given the widespread success of its big-screen counterpart in Marvel's The Avengers last year, millions of people were bound to at least check out the first episode only to realize it wasn't nearly as exciting, right? So, as the thinking went, it would seem to make sense if Agents of S.H.I.E.L.D. continued dropping as more established popular shows like NCIS resumed their usual domination.

Agents of S.H.I.E.L.D. might be stickier than you think
But then, in true superhero fashion, the left for dead Agents of S.H.I.E.L.D. on Tuesday did the unthinkable with its third episode: It came back to actually beat NCIS by a tenth of a ratings point with a 2.9 in the coveted 18-49 space. What's more, Agents of S.H.I.E.L.D. also came just a tenth of a point behind The Voice.

To be fair, however, both NCIS and The Voice still boasted a higher total number of viewers last Tuesday at around 18.3 million and 10.2 million, respectively, compared to the only 7.9 million viewers who turned on Agents of S.H.I.E.L.D the same night. 

However, we should remember there's a reason television ratings place so much focus on shows' abilities to maintain the attention of the disproportionately valuable 18- to 49-year-old demographic.

And that's not only great news for excited comic book enthusiasts who now have a compelling reason to tune into prime-time television, but it also obviously bodes well for Disney investors.

Remember, as I pointed out in August, Disney stated last quarter its ABC network remained the one weak link in its massive Media Networks segment, which collectively accounted for more than 46% of the company's total sales and 68% of its operating income in fiscal Q3.

In the end, though, regardless of how many people ultimately tune into Agents of S.H.I.E.L.D. every week, you can bet Disney will be happy to keep it on air as long as the show can continue winning where it counts.

So rejoice, Marvel fans, because I think the fun is only just beginning.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.