- Prior to the 90s DC Versus Marvel series, all other crossovers between the two companies were written as if the characters had always lived in a shared universe and been aware of the existence of the other company's locations and characters (the MST3K Mantra was in full effect). Avengers/JLA actually provides a possible belated explanation for this, as The Grandmaster's plan does indeed create a shared universe in which Marvel and DC characters are aware of each other and cross over regularly. Due to the nature of retroactive alterations in time, Superman vs. Spider-Man, Batman vs. Hulk, Teen Titans vs. X-Men and all the other prior crossovers can be seen as taking place in that alternate shared universe.
- There is a pre-existing explanation for these crossovers: The Unlimited Access mini-series revealed that universes tend to temporarily fuse in "crossovers", not only in the present day but also in the past, so Access must travel in time to ensure the universes re-split after each crossover to prevent them from becoming the Amalgam Universe again, with everybody forgetting such crossovers after returning to their own universes (this miniseries also included a previous JLA-Avengers crossover between the founder members of both teams).
- The Official Handbook of the Marvel Universe has numbered at least one Earth in the Marvel Universe (Earth-7642, to be specific) where the DC characters exist and regularly cross over with Marvel's characters; it's where Marvel canon places all of the crossovers aside from Marvel vs. DC and JLA-Avengers. The latter, at least, is implied to have involved Earth-616, the main Marvel universe.
- Superman would defer to Captain America after he's able to keep himself under control. After all, Superman's motto is "Truth, justice and the American way." Also, the Justice League has no leader, rather more of a council of charter members. The Avengers have more of a hierarchy.
- Superman is able to briefly wield Thor's hammer because Odin temporarily lifted the worthiness enchantment. Thor clarifies that Odin is "stubborn, not stupid," and given the circumstances, this can occur. Delve into it further, and this makes even more sense; when the entirety of both realities are at stake, literally ''anybody'' who wants to save it would actually be worthy.
- Superman "catches" Mjolnir in a way that would indeed allow him to stop it — he uses the maximum amount of surface area against the broad, flat part of the hammer. Had Mjolnir featured a blade or a sharp end (like its Ultimate version does), he would not have been able to. The force of the blow probably did hurt him, but Superman could handle it, since it didn't damage him.