There Were Three Rules Batman: The Animated Series Tried To Never Break
Back in the '30s, Bob Kane and Bill Finger's Batman was a lone "creature of the night," to quote Bruce Wayne in "Detective Comics" #27. But this creature didn't spend too long in the shadows before DC comics decided to drag him into the light. By the 1950s and '60s, Batman had become a much more light-hearted figure, battling all manner of fantastical foe.
In August of 1958, the Caped Crusader of the silver age could be found on the cover of "Batman" #117 donning his jet skates and facing off against an intergalactic antagonist in "Manhunt in Outer Space." Then there's the time Batman and Robin's dog, Bat-Hound, gained super powers in "Batman" #158. At one point Bats and the Boy Wonder were even turned into "two dimensional people" by the sinister 'Rainbow Creature' that served as the foe of Batman #134 in 1960. Increasingly reliant on these outlandish sci-fi narratives, the Batman comics fell out of favor with readers. In fact, if it wasn't for Adam West further galvanizing Batman's campy aesthetic with the famous 1960s TV show, the character could very well have disappeared from pop culture altogether.
Over the course of the '70s and '80s, Batman would regain much of the darkness that originally defined him. Thanks to writer/artists like Frank Miller and to some extent Neal Adams, the Dark Knight was on his way to reasserting his status as the "creature of the night" he once was. But it would take a children's cartoon of all things to really get him back to his roots. And when "Batman: The Animated Series" debuted in 1992, the creators went to every effort to make sure the character's days spent battling bizarre beasts and contending with superpowers stayed firmly in the past.
The Batman Bible
Show creators Bruce Timm and Eric Radomski had set out to create something truly unique with "Batman: The Animated Series." From the outset, the pair envisioned a much darker take on the character than was typical for children's programming at the time. It wasn't long before writer Paul Dini added his spin on the whole thing, bringing in the now famous elements of film noir and even using Alfred Hitchcock for inspiration. He also contributed to the "show bible" which codified the rules to follow when creating the show's look and narrative.
On top of all that, as writer and producer Alan Burnett recalled in Vulture's oral history of the show, there were three distinct rules that kept "Batman: The Animated Series" within its gritty, noirish bounds. Those rules were the antithesis of the silver age tales that had taken Batman so far from the darkness that defined his inception:
"We had these three rules: No aliens. No ghosts. And no Humanitas Awards — you know, no pro-social stories. We were just out to have a good time and to give the audience some fun thrills."
In their efforts to keep the show firmly within the limits of their shadowy aspirations the entire "Animated Series" team had, from the outset, ensured no 'Rainbow Creatures' or intergalactic adversaries would show up in their show. In doing so, they had effectively written that whole era of Batman's history out of their particular canon, in a move that proved hugely successful for the show and Batman as a popular icon. As Writer Rich Foegl says in the "Heart of Batman" documentary, he and his cohorts had "scrape[d] off all of the barnacles of the storytelling that have accumulated over the years," and got back to "the essence" of Batman.
Bending the rules
You can find the "show bible" for "Batman: The Animated Series" online if you do a quick search. It unsurprisingly contains references to a "darker look and tone" and "hard-edged crime drama" as well as directing writers to of avoid "tongue-in-cheek campiness." And while the three rules that Burnett mentions don't appear explicitly in the bible, the whole thing is basically a manual for protecting against everything that almost drove Batman out of the mainstream in the mid-20th Century.
That's not to say "Batman: The Animated Series" stayed wholly away from the fantastical. Supernatural villains such as Clayface were big parts of the show, which often seemed to test the limits of its own rules by introducing characters such as the werewolf in underrated episode, "Moon Of The Wolf." There's also Garth the ape man and Tygrus the humanoid tiger creature from what might be the most ridiculous "Animated Series" episode "Tyger Tyger." And the show literally kicks off with one of the less grounded Batman villains in the form of Man-Bat in the first episode "On Leather Wings." Still, he wasn't an alien or a ghost or a metaphor for some societal issue that needed resolving, so the rules remain technically unbroken.
Those instances aside, there's no doubt Timm and Radomski's series maintained a commitment to the dark origins of Batman throughout, which played a major part in the show becoming as celebrated as it is. It's not quite Nolan levels of cinematic reality, or Reeves-level grittiness, but it was serious and grounded enough to help rehabilitate Batman's status as that "creature of the night" from "Detective Comics" #27.