The concept of “crossover” is a very strange and relatively modern one. I imagine that, in ye olde dayes of yore, a storyteller who wanted to have Heracles meet Gilgamesh didn’t have to create a time-vortex omniversal space/time breach to do so (or in the case of Angela’s recent Marvel Universe debut, a ten-issue plotless boondoggle) she probably just said “Okay, this one time? Two guys totes met, y’all…” Audiences and storytelling tropes have gotten more sophisticated over the centuries (for better and for worse) and as a result, today’s readers want explanations to rationalize why Spider-Man wouldn’t participate in the Crisis On Infinite Earths. Luckily, with modern corporations slowly merging into Skynet, the likelihood of unusually diverse holdings and potential team-ups increases, such as the new reality of Wolverine, Fozzy Bear, Chewbacca and Goofy sharing rights-holders and thus being able to team up as “Fuzzy Feller Force! (The rejected options were “Wocka Warriors”, “GROOOAAAAOOWR”, and “SniktBubBubBubSnikt.”)
The MS-QOTD (pronounced, as always, “misquoted”) still wonders if Age Of Ultron wasn’t actually created to reveal Miracleman, with the Angela debut a necessary legal compromise, asking: How much setup is really necessary for a crossover-type story to work? Can Superman and Spider-Man just meet up and start punching Alex Luthor?