Welcome to another installment of Easter Eggs in Comics! Click here for the archive!
In July 2006, Marvel Comics launched what was then their big event, CIVIL WAR, in which Captain America leads an army of superheroes against Iron Man, who has his own army of superheroes.
A few months before, DC was in the middle of what was then their big event, INFINITE CRISIS, in which a villain named Alexander Luthor created a new multiverse with the intention of finding the perfect earth. The new multiverse has earths with numbers for designations (Earth-1, Earth-56, Earth-254, etc.), and Alex plays mad scientist with them, picking worlds and mixing them, and discarding it when it doesn't work.
Here he is, mixing Earth-154 and Earth-462.
What do those numbers add up to? 616. You see, in the Marvel multiverse, the parallel earths are also designated by number, and the main Marvel earth, the one we read about, is Earth-616.
So let's see what Alex Luthor's experiment turns out as, shall we?
Get it? The heroes of Earth-616 are fighting amongst each other. It's a civil war!
A few years later, DC put out their next big event, called FINAL CRISIS. It had a lot of tie-ins, including one called SUPERMAN BEYOND, where Superman travels across the multiverse to save it from destruction. Here's a glimpse of one earth he passes by.
Those are some thinly veiled analogues of Marvel heroes, folks! Their Civil War came a few years too late.
Travis Hedge Coke points out to me that "Iron Man" being an alien may be a reference to Marvel's big event then, SECRET INVASION, which involved the shapeshifting Skrulls coming to Earth and replacing some of Marvel's heroes.
So you got a two-fer this time, folks!