...and I just noticed a big one. I was thinking about "Rock of Ages", the classic JLA storyline from the mid-90s penned by Grant Morrison. For those of you who are unfamiliar with the story, it involves Lex Luthor reforming (or forming--DC continuity was still a little unsettled back then) the Injustice Gang as a group of "all-star" villains to take on Morrison's "all-star" JLA. Luthor has an ace up his sleeve, too, in the form of a powerful artifact called the Philosopher's Stone with reality-warping powers.
But even as most of the League takes on the Injustice Gang, a few heroes have gotten shanghaied by Metron to the future, where it turns out that Darkseid has taken over the world and enslaved its populace into mindless drones with his Anti-Life Equations. Worse yet, it turns out that the cause of all this was the destruction of the Philosopher's Stone at the hands of the JLA...defeating the Injustice Gang in the present is the beginning of Darkseid's ultimate triumph.
Needless to say, it's all resolved well. The heroes escape back to the past and stop Superman from crushing the Philosopher's Stone, the JLA defeat the Injustice Gang anyway, and everything is right with the world.
Now, fast forward a little over a decade. Morrison's star has risen, fallen, and once more risen with DC, and he's in position to write what they're marketing as the ultimate crossover, the big Darkseid epic to end all big Darkseid epics, the so-called "Final Crisis". In it, Darkseid's plans are finally coming to their ultimate fruition; he's got the Anti-Life Equation, he's destroyed or corrupted the New Gods, and he's ready to crush all free will in the universe and turn everyone on Earth into his mindless drones. And of course, the only thing that can stop him is...
Wait, what? The Miracle Machine? Seriously, Morrison? You ignore an absolutely perfect piece of foreshadowing that you yourself set up eleven years in advance in order to stick in an obscure continuity reference that only a handful of fans will even recognize?
Alright, nobody ever gets to complain about Mark Waid's hard-on for the Silver Age ever again.