The writers of the show are obviously comic book fans. Aside from the show creator doing Supergirl/Batgirl shorts for Cartoon Network, there are a bunch of obvious nods to geek-centric things like Spider-man, Batman, Hulk, Star Wars, Star Trek to more obscure stuff like The Big Lebowski. So it's a safe bet that many of them have been reading comics over the last two decades.

The show is definitely written to be more than all-ages friendly, especially the first season which was made under Educational/Informational standards that outlined stricter censorship and more ridged story structure with the moral outright recapped at the end of each episode.

And yet the older fans find a ton of subtext in the show, and I don't think it's (just) their obsessive nature filling in things that aren't there. Just as Kurt Busiek started a trend of reexamining classic silver age stories and injecting more depth and modern storytelling styles into the spaces between panels in the somewhat simpler narratives of the 60's, so too are the writers of these simple happy pony tales leaving openings with hints of bigger, more complex stories than they'll ever get into on the show itself. Only instead of injecting new interpretations into older stories, they're preloading the hints of such things into scripts as they're written.

I think it's a shift that has come from the influence of the years of pop-culture remaking childhood favorites into entertainment for an increasingly older and more sophisticated age-range. I think the writers see where the openings for more complex interpretations would be, and that the older geek audience has been trained to see those hints as well.

And so, to my little cousin and nephew, Pinkie Pie is a zany, lovable, "crazy" character while myself and a large percentage of older fans see Pinkie as funny and lovable but tinged with a bit of sadness because she's not just zany... she's literally insane, and her constantly upbeat attitude is something of a coping mechanism.

The thing of it is, they know better than to ever take away the lovable, zany character the kids see and love in favor of a darker, more complex version. The hint is there for adults; a little peek behind the curtain before it's closed up and never mentioned again. Comics seem to have forgotten how to toe that line, and have robbed too many characters and stories of their innocence in the process.