Superhero crossovers, whether they’re in comics, film, or television, are often subject to a considerable degree of critical scrutiny, with detractors arguing that they are overly busy attempts to drive up sales or viewership. But while financial benefits certainly play a part in motivating most crossovers, and some of the weaker ones do come across as little more than cash grabs, they’ve also become an integral part of the genre. Especially in Marvel and DC Comics, crossovers happen so frequently that many different characters have become essential parts of one another’s stories. One of, or possibly the most popular, aspects of the Marvel Cinematic Universe is that it brings this element of the comics’ storytelling to life and was the first to do so on the scale it does.