One of my favorite conceits in all of comic book-dom, I think introduced in Busiek-Perez’s JLA/Avengers, is that in the D.C. Universe, the Earth itself is physically slightly larger to accommodate all of DC’s crazy-assed fake cities and countries.
It kind of ruins the contrarian fun of speculating that Gotham was an analog for Detroit or Philadelphia or—fingers permanently crossed—Chicago, but then again, I also had a DCU Roleplaying Game handbook when I was a kid that said Metropolis was in Delaware, so who cares I guess.

“Galactus, eat them first, they’re bigger.”
The Basics: Marvel’s 3-D Man and Doritos® Collisions®


