As the 1960s turned into the 1970s, two things were going on in the world of comics. Upstart publisher Marvel was gaining ground on its rival, the massive DC Comics, then known as National Periodical Publications. And a new generation of creators was coming into the field, one that had grown up reading comics as fans. And as fans, this led them to want to see their favorite characters from both companies in the same adventure together. On occasion, this impulse would result in the creation of an unofficial “stealth crossover” orchestrated by the creators on books at the different outfits, always without the knowledge of the higher-ups. Here then are the five best unofficial Marvel/DC crossovers.
AVENGERS #69-70/JUSTICE LEAGUE OF AMERICA #75: This is perhaps the first of the unofficial crossovers between companies, and reputedly it was an idea hatched at a party where alcoholic beverages were in ample supply. The prime mover was apparently Marvel writer Roy Thomas, which is no surprise given his fannish leanings and his love for the DC characters. He conspired with JLA writer Denny O’Neil to do a stealth crossover between their two titles, as Roy was heading up AVENGERS during that time. And indeed, as part of a cosmic chess match between the Grandmaster and Kang, the Avengers find themselves locking horns with the Squadron Sinister, who are clear analogues for the main four Justice League members. On the other side of the fence, Denny apparently didn’t think he’d be able to sneak much of anything past editor Julie Schwartz, so rather than including Avengers counterparts, he created a group of illusory Justice League phantasms, each of whom describes themselves at some point as an analogy to an Avenger–the Batman figure uses a trash can as a shield, for example, and the Superman fantasy-figure compares himself to the thunder god Thor. As such, it’s not much of a crossover, but it got this whole thing started.
AVENGERS #85-86/JUSTICE LEAGUE OF AMERICA #87: A little over a year later, Roy was ready to try again, this time with a counterpart who was either more willing to go along or more heedless of the danger should his editor call him out on it. So in AVENGERS #85-86, the Avengers find themselves trapped on a parallel world inhabited by another version of the Squadron Sinister–only here, these guys are heroes, the Squadron Supreme, and their ranks include additional heroes based on other JLA members. Meanwhile, over in JUSTICE LEAGUE #87, new writer Mike Friedrich had the League run into an unnamed team of heroes from the planet Angor–heroes who similarly mirrored and evoked their counterparts in the Avengers. So this worked out much more along the lines of what Roy had in mind.
AQUAMAN #56/SUB-MARINER #72: This was a different kind of crossover, but one that is unique and interesting in its own way. In AQUAMAN #56, writer Steve Skeates had begun what he’d intended to be a multi-part story, only for the series to be cancelled with that issue. He hastily reworked his ending in order to not leave the story on a complete cliffhanger–but he still liked what he had intended to do in the second part. A few years later, SUB-MARINER was also being cancelled, but it had one final issue unaccounted for on its schedule, so Skeates was brought in to write it. And he made it a sequel to AQUAMAN #56, picking up on the quasi-cliffhanger he had left years before in another title entirely. The crossover is made overt by the fact that, in AQUAMAN, the Sea King presses a button to destroy a satellite that is playing havoc in his story–and in SUB-MARINER, we see that same panel of a gloved hand pushing a button to destroy a satellite which sets off the threat that Namor must need to contend with. This became one of those fan secrets that delighted the audience as sharp-eyed readers determined the link between these two final issues.
THOR #207/JUSTICE LEAGUE OF AMERICA #103/AMAZING ADVENTURES #16: Rutland, Vermont had grown famous in comic book fan circles for their annual Halloween parade, which for years had been supervised by super-fan Tom Fagan, an enormous Batman fan who fielded floats featuring numerous people in super hero costumes. It became such a destination site for the young creators in the industry that it started to show up in actual stories, such as AVENGERS #83 and BATMAN #237. But this was the trifecta. In this particular year, Gerry Conway, Len Wein, his then-wife Glynis Oliver and Steve Englehart took a trip up to Rutland for the Halloween party, and then fictionalized their adventures across three comic books published by two companies. All four creators show up in all of these books, and each one tells a portion of their adventure–and Steve Englehart’s car is critical to one of the stories. In addition, there are cameos from party-goers dressed in costumes of the other company’s characters–in fact, when JUSTICE LEAGUE OF AMERICA #103 was reprinted several years later, somebody was uncomfortable with just how close the Marvel characters appeared to the real thing to go back into it and change them somewhat.
INVADERS #14-15/FREEDOM FIGHTERS #8-9: Having gotten away with it twice, Roy Thomas tried his luck one more time in the mid-1970s, while he was working on INVADERS. Here, his DC co-conspirator was writer Tony Isabella, who had come into the field under Roy’s tutelage. So over two issues of both INVADERS and FREEDOM FIGHTERS, the respective heroes found themselves clashing with new groups of heroes–in each case called the Crusaders–who turned out to be the dupes of villains. And each group of Crusaders paralleled the characters in the other series. Isabella took the joke further by making the four young fans that the Silver Ghost turns into the Crusaders in FREEDOM FIGHTERS be caricatures of Marvel’s editorial staff, including Roy himself.
ADDITION: In the comments, Tony Isabella correctly points out that while he came up with the idea for this last unofficial crossover as editor of FREEDOM FIGHTERS, it was writer Bob Rozakis who actually executed it, working for the following editor Jack C. Harris. This is what I get for relying on my imperfect memory too much.