- Complete Monster: Krona is a former Oan scientist and callous egomaniac who desires to learn the secrets of the universe, and later goes on to destroy countless universes to discover their creation. Arriving in the Marvel Universe, he makes a bet with the Grandmaster, to put the heroes from their universes against each other to collect a dozen cosmic items. When Krona loses, he reacts by fatally torturing the Grandmaster, before summoning Galactus and killing him in a fit of rage. Using Galactus's corpse as a new base of operations, Krona learns of the sapience of the two worlds—Eternity and Kismet—trapping the two beings together to learn their secrets. When Metron calls out Krona for caring about conquest as opposed to knowledge, Krona eventually admits to this. Hoping to recreate Galactus's origins with himself in his stead, Krona plans on forcing the Marvel and DC Universes together to destroy them both and start a new Big Bang.
- Crack Pairing:
- Eternity and Kismet fall in love over the course of the story. Seriously. They are the living embodiments of the Marvel and DC universes, respectively. Incredibly, their embrace as Krona tortures them and their visible sadness when they are finally separated are actually pretty moving. Note that pairing them with anyone else but each other would be even more of a Crack Pairing.
- Hawkeye and Black Canary are an item together briefly while the universes start to collapse on each other.
- Designated Hero:
- Superman is a Jerkass for most of the crossover, not The Cape as he's normally written.
- Captain America was also written this way — it was given a vague explanation about the two heroes who were most closely tied to their own respective worlds being the most unnerved by the change in their accepted reality.
- The universes also have differing physical properties. At one point, Superman comments that sunlight in the Marvel universe feels "greasy", which probably added to his irritation.
- Dork Age: Leave it to Kurt Busiek to make a compelling story point out of these. In the third chapter, the heroes are in a happy Silver Age-style two-earth universe, and once they finally realize that this is just a distraction as the Earths destroy each other, they ask to see the worlds the way they should be. Each character sees the Face-Heel Turns, Heroic Sacrifices, Suspiciously Similar Substitutes, and With Great Power Comes Great Insanity that they will experience in the "correct" universe. They are horrified and initially consider the selfish idea of just leaving the Earths as is. Finally Hal Jordan, who arguably has the most to lose, tells everybody that they don't have the right to play God with the Earths (which, ironically, was the root of his own Dork Age), and the heroes agree to restore everything that was, both good and bad.
- Fanfic Fuel: The Justice League and the Avengers having frequent cross-dimensional visits, similar to the pre-Crisis JLA/JSA team-ups.
- Harsher in Hindsight: Barry saying that he didn't mind dying because Wally West was holding up the Flash legacy. Then came the New 52...
- Hilarious in Hindsight: And Harsher in Hindsight In-Universe — Hal Jordan says that the JLA and the Avengers shouldn't try to "play God" with their realities and try to make them the ones they want. Cue DC Rebirth, when a Godlike character has been revealed responsible for doing just that in creating the New 52.
- Moral Event Horizon: Most of the villains Krona summons to battle the heroes are a bunch of dumb thugs. But Dreamslayer decides that Hawkeye and Flash are inspiring their friends with their good humor, and coldly disintegrates them with a magical blast. Don't worry, though. Dreamslayer and his associate Doctor Diehard get some Laser-Guided Karma courtesy of cosmic-powered Kyle Rayner. Theirs are the only graphic deaths in the story. It helps that Dreamslayer is a being of pure magic, and that Doctor Diehard is a robot.
- Never Live It Down: Grandmaster shows the heroes the hardships they will endure if they restore reality to its proper state. Take a wild guess at what Hank Pym sees.◊
- One-Scene Wonder:
- The Thing only appears for two pages, but absolutely steals the show by just being his ever-lovin' self, rendering Batman speechless until he leaves. After this the stunned Dark Knight has to admit that Grimm has a "rough-edged charm" all his own.
- Despite the high stakes nature of the crossover, Hulk only makes a brief cameo in the final battle.
- Shocking Moments: This whole series is made of these.
- Thor hits Superman with his hammer, Supes catches it.
- Krona defeats Galactus... And then builds a house out of him.
- The Epic Battle scenes are pretty incredible too, especially for hardcore fans (one panel shows Superman going one-on-one with Count Nefaria)
- Parallax briefly returns, and thankfully, he's not around long enough to do his unique brand of damage.
- Darkseid wearing the Infinity Gauntlet... fortunately, it doesn't work in the DCU.
- They Wasted a Perfectly Good Plot:
- An intentional example, with the various Marvel vs. DC crossovers shown in one panel (like Lobo vs. the Shi'ar Imperial Guard) or only alluded to.
- Darkseid with the Infinity Gauntlet alone would've had limitless possibilities.
- As great as the miniseries was, the fact it was about specifically those groups meant that other major characters from those universes (such as the JSA, X-Men, Spidey, Daredevil, Teen Titans, New Gods and Fantastic Four) only appeared briefly. Thankfully, those appearances were usually quite awesome. Batman fighting The Punisher (off-panel) and the drug dealers he was shooting up, anyone?
YMMV / JLA/Avengers