When I heard that DC Comics was planning a series of prequels to Watchmen, my first reaction was the one seemingly shared by most fans of the seminal graphic novel: “For the love of God, why?” Satirists have had plenty of fun contemplating the schlocky derivatives that might be spun off Alan Moore’s masterpiece for the sake of a quick buck, but it had gone unsullied so long that many of us had begun to imagine that taste might have scored a rare victory over avarice this time around.

My second thought also appears to have been fairly common: Moore is probably the last person in any position to wax righteous on this point. With the conspicuous exception of V for Vendetta (and arguably the historical fiction From Hell) his most famous works have involved re-imagining characters created by others. Moore cut his teeth on Mick Anglo’s Marvelman (AKA Miracleman), and was introduced to American readers by his brilliant run writing Len Wein’s Swamp Thing. His Lost Girls cast beloved heroines of children’s literature in what Moore himself characterizes as “pornography,” while The League of Extraordinary Gentlemen mashes up classic pulp adventure stories to give us a 19th century Avengers, with Mr. Hyde, Captain Nemo, and Allan Quatermain filling in for the Hulk, Tony Stark, and Captain America. Watchmen itself was originally supposed to star a roster of Charlton comics characters that D.C. had acquired, including Steve Ditko creations Captain Atom and The Question (ultimately reimagined as Doctor Manhattan and Rorschach).

My third thought, however, was that  looking at why he didn’t end up using those original Charlton characters—and instead giving us their vastly more interesting close cousins—might shed some light on why fans are so dismayed in this case by the quintessential comics ritual of passing an iconic character to a new generation of writers. The problem was that it quickly became clear to the honchos at DC that Watchmen would break their new toys. It would have ended with (spoiler alert) Thunderbolt as a mass murderer, The Question a bloody smear in the snow, Blue Beetle as an aging husband, and Captain Atom an autistic spacegod. These were not promising starting points for ongoing use of the characters.

The classic comics solution would have been to simply set the events of Watchmen in an alternate continuity or parallel timeline, leaving the mainstream versions of the characters untouched, but at the time, D.C. had just launched its Crisis on Infinite Earths, which was to climax with the compression (since undone) of D.C.’s increasingly cluttered multiverse into a single, more manageable universe. Even had that not been the case, though, it seems inevitable that either (1) the power of Watchmen would have been diluted by relegating it to a mere “What If” story about characters who continued to have “ordinary” superhero adventures in main continuity, or (2) more likely, the power of the Watchmen narrative, and the characters’ actions and attitudes within it, would have overwhelmed any later attempt to portray them differently.

This ultimately brings us to an important distinction between standard, self-contained fiction and what I’m inclined to call “Extended Universe” narratives. By “Extended Universe” fiction, I mean the growing body of fictional continuities that are understood to provide a unified context—though just how unified varies from case to case—for stories told across many years or decades by many authors working in many different media. The two major comic book universes—D.C.’s and Marvel’s—are obvious examples, as are the various tangled continuities of Star Wars, Star Trek, Doctor Who/Torchwood, and perhaps Joss Whedon’s “Buffyverse,” among many others. The larger background story is often referred to as a “mythos,” which seems appropriate enough, because one of the earliest forms of human narrative—myth—embodies just this kind of collaborative, cross-generational storytelling.

What these have in common is that they’re united—however unstably—by the idea of a single “official” or “canonical” continuity that isn’t necessarily tied directly to a single creator. If you look, by way of contrast, to the Sherlock Holmes stories, everyone agrees that the “canon” consists of the original novels and short stories written by Sir Arthur Conan Doyle. If Alan Moore or Nicholas Meyer or Michael Chabon or Guy Ritchie later decide to tell new stories involving Doyle’s characters, we understand these as new and independent tales, which don’t affect what “really” happened to Holmes in the original story.  By contrast, if later writers decide, with the blessing of the official keepers of continuity, that James T. Kirk’s middle name is “Tiberius,” that Spider-Man’s parents were secret agents, or that Green Lantern rings are vulnerable to the color yellow because of a demonic impurity, then that is the “real” version of events and always was—even if the original authors of those characters hadn’t envisioned any such thing. This is why Star Wars fans reacted with such annoyance at George Lucas’ decision to explain The Force as a scientific rather than a spiritual phenomenon, generated by microscopic “midichlorians”: Because Lucas can issue an “authoritative” decree that changes how the events of the beloved original trilogy are to be interpreted and experienced.

Some such considerations appear to have transformed Moore’s own attitude toward film adaptations of his work. His initial reaction was professed indifference to movie versions: The comic is the comic, and stands on its own, untouched by however good or bad a movie might be. His shift from indifference to hostility may reflect a recognition that this isn’t really the case, at least when the movie version is perceived as The Movie Version—a unique, official cinematic rendering, as opposed to simply one of many possible motion picture interpretations. If it’s The Movie, then however Doctor Manhattan’s voice sounds there (for instance) is what the character “really” sounds like in many people’s minds.

This might all seem a little silly: Obviously none of this stuff “really” happened, and so individual fans are free to disregard the events of the Star Wars prequels if they so desire. For that matter, they’re free to hit “pause” fifteen minutes from the end of Jedi and imagine (or film) their own ending where Luke and Vader do join forces to overthrow the Emperor and rule the galaxy as father and son.  But fiction becomes more credible and immersive when we abandon a measure of control—imbuing it with the same obstinate independence as physical reality.  And that means, in part, surrendering to local conventions about what counts as a “true” event within the extended narrative, as opposed to (say) fanfic or authorized “alternate” versions. (The lines, of course, are blurry. Batman: The Animated Series took place outside mainstream D.C. continuity, but the character of Harley Quinn and the vastly-more-interesting revised origin of Mr. Freeze were both rapidly imported from the former into the latter.) And all this, I think, brings us back to what  bugs people about prequels to Watchmen.

Whatever uncertainty there may have originally been for the audience, Alan Moore told a superbly self contained story with exactly the right amount of narrative negative space. Few authors have as Moore’s finely tuned sense of the unique powers of comics as “sequential art”—frozen images where the “action” is provided by what readers supply to fill that razor thin, infinite gap between frames. But this is true in some form or another whatever the medium, as every good storyteller knows. It’s what renders the sequence excerpted above—maybe my favorite in the whole of Watchmen, though competition’s stiff—so powerful. What if Jon had stayed to explain his remark? What if we’d continued to a tedious illustration of exactly what he meant, and how inevitably Veidt’s hard won peace would decay? It would be inane; the scene works because all that is left implicit.

Like its own central chapter “Fearful Symmetry,” this is a narrative in exquisite, delicate balance. And why is it constructed that way? Because Moore didn’t use the Charlton characters. Because the Charlton characters had to be good for further adventures, but the protagonists of Watchmen (who are not, nota bene Dan DiDio, called “The Watchmen”) could be single use. And everything about the reader’s experience of the book turns on this being the case—on Watchmen not being, as many superhero comics are, a chapter in a series that continues indefinitely. That “Nothing ends Adrian” gets its power because we understand that Manhattan’s denial actually is the end of our story—that there isn’t any “Stay tuned for issue 13, where we find out just what Jon meant!”

In other stories, the reverse is true: Batman defeats the Joker—again, and we knew he would–but never for good. He’ll escape from Arkham and the battle will start over, because the only final victory of order over chaos is the heat death of perfect, entropic equilibrium. Like a Wagner motif, it doesn’t have its full meaning in isolation, but only as one permutation in a series. Pick your favorite Batman/Joker story, and suppose it really ends there: Joker dies (for good!), Batman maybe beats up on ordinary thugs for a couple years before a silver-haired Bruce Wayne retires or finally succeeds in joining his parents. However masterfully written that last story is, it would be a cheat and an anticlimax. To say (as we accurately do) that their conflict is iconic is just to say that it transcends the specific: It’s always still happening now, whenever you’re reading. Nothing ever ends.

The real trouble, then, isn’t so much that nobody should ever do to Alan Moore characters what he did to Arthur Conan Doyle and Bram Stoker and Jules Verne’s characters. The trouble is that Moore told a self-contained story in a corporate and cultural context where the Extended Universe narrative is the norm, and where readers are primed to treat continuations of a story, if they have the proper institutional imprimatur, as “real” for that fictional context. Nobody reads The League of Extraordinary Gentlemen back into 40,000 Leagues Under the Sea in any comparable way.

The irony here is that you actually could have sequels and prequels and parallel versions of Watchmen without damaging the reader’s experience of the original.  It’s just that D.C. Comics can’t be the one to do it, because the narrative worlds would be too close to keep them from colliding—a recipe, as every D.C. reader knows, for a Crisis.