This was originally posted over at TV Tome. Thought it would be useful to be posted here. it's just info - no need to post or comment on this thread, as it is for info purposes to explain some of the Analysis stuff when we get it up.
Justice League – What is “Crisis?”
What was the Crisis?
Crisis on Infinite Earths was a 12-issue comic book maxi-series published in 1985 and 1986 in which DC Comics condensed their multiverse into a single universe, thus "simplifying" and "improving" it. Whether they succeeded in that goal is a good question, and one I shan't address. Crisis is, however, incredibly important to understanding DC continuity, as well as being possibly the most significant crossover series of all time. It's also a fine story, in my opinion.
Why did DC need a Crisis?
In the late 30s, 40s, and early 50s the company that would become DC Comics published a great many superhero titles, featuring characters such as Superman and the Flash (Jay Garrick). Many of them were members of the Justice Society of America. This era is now called the Golden Age. In the late 40s, superhero popularity declined, and through the mid-50s only Superman and a precious few other heroes remained in publication. In 1956, a new Flash (Barry Allen) was introduced, inaugurating the Silver Age of comics. Barry Allen was in part inspired to become "Flash II" by the comics he had read as a child; comics about Jay Garrick, "Flash I". Flash II later joined the Justice League of America, alongside Superman, who was, of course, still around.
See the problem? Superman had fought beside Flash I; Superman was now fighting beside Flash II. But, to Flash II, Flash I was a fictional character. The "fictional" aspect was addressed a few years later, in the pivotal story "Flash Of Two Worlds" (Flash #123). In it, Flash II accidentally "tore a gap in the vibratory shields separating [two] worlds", and traveled to an alternate Earth, one where the retired Jay Garrick lived. When asked how Barry could possibly have read about Jay's adventures, Barry replied, "A writer named Gardner Fox wrote about your adventures -- which he claimed came to him in dreams! Obviously when Fox was asleep, his mind was "tuned in" on your vibratory Earth!"
Only a couple years later, Mr. Fox decided to pull out all the stops. In Justice League of America #21-22, he presented us with the stories "Crisis On Earth-One!" and "Crisis On Earth-Two!", in which the Justice Society and Justice League teamed up to foil a cross-Earth group of villains who had found a way to bridge the gap through music and magic. The issue of the "identical duplicates" was ignored - Superman did not appear to remember having been a member of the Justice Society, for instance. The Silver Age Earth of Barry Allen was dubbed "Earth-1", and the world of Jay Garrick, "Earth-2". This is important and counter-intuitive: The older Flash I was from Earth-2, and Flash II was from Earth-1.
At the very end of the adventure, as the heroes are closing in on the villains, their thoughts turn to escape, and the Fiddler cries out, "There is an Earth-One and an Earth-Two! Somewhere there must be an Earth-Three! If we can find the doorway into it -- before the justice champions find us -- we can escape them forever!" They did not find it in time, but the seed of a multiverse was planted.
The basic story of the Crisis is that a shadowy figure called the Anti-Monitor is bent on destroying all versions of the universe and an equall shadowy character called the Monitor is trying to stop him. So he recruits the heros of the multitudes of Earths, meaning at least 2 Supermen, Batmen, etc. The series includes, I think, every DC character not already dead, many of who I've never heard of. In the end, all the versions of Earth are collapsed into one continuity, killing off billions of people on those planets as well as many superheroes and supervillians, including several versions of Lex Luthor, a Lois Lane, the Flash II - Barry Allen I think, a Supergirl, a Robin, and, of course the Monitor and Anti-Monitor to make it seem like nothing happened when the realities collapsed into themselves into what is called Earth Sigma.
All in all, this didn't help since in the mid-90's DC released Zero Hour, which tried to fix the Crisis's flaws. But writers are writers, and they will write what they want to make a story good. I personally don't care about continuity, I have never read the Crisis series and don't plan to, the only reason I know about it is from the Simpsons episode guide called "The Simpsons Forever, where in the episode "Worst Episode Ever," parodies the cover of issue 7 of the series when Supergirl dies, but if you want the whole story you can pick up the bound copy of the series that are floating around in your local comic store.