Back in the Silver Age (when I was a kid) DC had Showcase and other places to try out new characters and see if they could support a comic book. Marvel tried out new characters in their sorta general anthology titles – Any Man/Giant Man started out in Tales to Astonish and Thor in Journey into mystery, for instance. They later set up Marvel Spotlight explicitly for testing new characters.
But sometimes they gave trial runs of characters elsewhere.
Supergirl got a tryout in Superman #123 from August 1958 . In “The Girl of Steel” Jimmy Olsen gets a wish granted, to create a female counterpart for Superman. He wishes her gone when he realizes she’s not such a great idea. The created Supergirl looked very much like the one introduced in Action comics #252 in May 1959, right down to the yellow hair, but when they reprinted the story later they changed her hair color to reddish and her costume to green and orange, maybe because they thought their readers would be confused between this first Supergirl and the later “real” character. (Of course, Supergirl got REALLY confusing as the 21st century approached, but that’s another story.)
Captain America – Before he was revived in Avengers #4, they gave Cap a sorta tryout in Strange Tales #114 (nov 1963) , where he fights Johnny Storm (The Human Torch) (Because, you know, the chief method of interacting between comic book characters is the dustup). It turns out to really be an old villain, The Acrobat, dressed up in a Captain America suit, with a round shield. Musta been interesting for Jack Kirby, who created the Golden Age Captain America and drew him then to do it again here (and in Avengers #4 in March 1964)
Conan the Barbarian – Before he got his own comic, Marvel gave Conan – or at least something so similar to him that you’d have to check the VIN to be sure – a tryout in Chamber of Darkness #4 in 1970. Barry Smith, who would be the first Conan artist (in both the Conan comic book and in Marvel Tales #1, which , not being a comic book, could have a little nudity – “The Frost Giant’s Daughter” – which they ran in the regular comic a bit later with the nudity covered up)
Exactly why they did these trials isn’t clear to me. The regular runs with the characters started so soon afterwards that they must have been in the works at the time. Did they ever do any sort of surveys to see how well these characters “tested”? What if they tested badly? Why did they only do these tryouts for a couple of cases (which looked like sure things from the start), and then go on and simply ran other characters with no tryout at all, sometimes throwing them right into their own comic?
I think the simplest explanation is marketing.
New Guy #1 is coming out next month.
This month, he will do a guest appearance in Old Guy #101.
Hopefully, millions of Old Guy fans will start buying New Guy.
Alternatively:
Old Guy’s author has writer’s block, and a deadline breathing down his neck.
He walks across the hall, and says, “May I use New Guy in my book? There will be a misunderstanding, they will fight a bit, then they will make friends at the end, and nothing will happen that will interfere with your storylines.”
New Guy’s author says, “Sure. We need publicity anyway.”
It turns out to be a complex story for the case of Conan. I woulda thought it was just a simple “run the sample Conan story and see how it flies. use the same artist!” But see this piece:
Another example of a character who had a “tryout” is Wolverine. He was originally created to be a one-shot opponent for the Hulk, appearing in The incredible Hulk#180-181 in 1974. The next year, a slightly reworked version of the character was one of the mutants recruited in Giant-Size X-Men#1.
They definitely could see how the one-shot character is received. Sales would be part of it (though it took awhile to get the numbers) as would letters to the editor. They could have something ready to go if sales are good – or, if surprised by the reaction, they could rush something out. Note that Batman showed up in Detective Comics in March of 1938 and had his own book in May of 1939.
It would have been simpler to create a new Supergirl comic in the time frame you mention. Remember, she was introduced in Action Comics as an eight-page feature. It wouldn’t take much time to rush out a story that length and put on a new cover.
I read that creating a new comic book title is somewhat more expensive than normal which was supposedly the reason characters like Thor, Iron Man and others premiered in horror/suspense comics that were already running.
It’s no more expensive than any run of comics, but you have no idea how popular it’ll be until the issues come out, so the chance of failure is great. Better to run a test in an existing book and see what the reaction is.
I note that March 1938 to May 1939 is over a year – 14 months. In the examples I cite above Supergirl had a gap of nine months between conception and being "born.
Captain America had only Four Months
The “Conan” tryout in Chamber of Darkness in April 1970 and the Conan comic came out in October, eight months later. From the write-up I cite above, Roy Thomas said that he didn’t actually have a Conan comic in mind when he scripted the tryout, because they were still arguing over cost to use the character.
I don’t know how long a comic production schedule is. I can accept that there was time to evaluate Supergirl and Conan between tryout and appearance, but that four month gap for Captain America seems way too short. I suspect they knew they were going to add him to the Avenger mix. (He didn’t get his own feature until November of 1964)
During that period (the early 1960s), Marvel’s comics were actually distributed by National Periodical Publications (owners of DC Comics at that time). This was a deal that Martin Goodman, Marvel’s owner, had negotiated back in the 1950s (when the company was called Atlas Comics), in an effort to save money.
Under the very restrictive terms of the distribution agreement, Marvel was limited to publishing only 8 comics per month. That was the primary reason so many of Marvel’s early heroes appeared in anthology books, and even shared books with other heroes for a time. They had more heroes than they had available books, and debuting a new series would have forced them to cancel an existing one. So Iron Man and Captain America both appeared in Tales of Suspense, while the Hulk and the Sub-Mariner shared Tales to Astonish, and the Human Torch and Dr. Strange shared Strange Tales. That’s also why so many of the series were published bi-monthly for awhile, so that different books could come out in alternate months.
It wasn’t until years later (1968 or so, I think), that Marvel was able to get out from under that restrictive distribution deal, and then they were able to greatly expand the number of series they published. That’s when all the heroes pretty much got a book of their own, and the anthology series more or less vanished.
The story I’ve heard is: back in the day, a publisher launching a new magazine had to pay for a postal permit to be able to mail/ship issues at a discounted rate, so it was often more efficient for a publisher to have a new feature take over the numbering from an existing title rather than start from issue one. The only caveat was that the title change had to have some continuity between the previous title and the new one. The classic example is All-Star Comics, home of the Justice Society of America, becoming All-Star Western in the late 40s.
Also, unlike today, when a comics company will cancel and relaunch titles willy-nilly to get a sales boost from a first issue, newsstand operators used to prefer titles with higher numbers, as they implied stability and longevity.
One could argue Firestar, who appeared next to Spider-Man and Iceman on a Saturday morning cartoon. Didn’t show up in Marvel canon until 4 years latter, and only really joined the fold with a mini-series a few years after that.
Similarly, Harley Quinn was originally introduced in Batman: The Animated Series in 1992. While she apparently made some appearances in comic books starting in 1993, those first appearances were in books that were considered part of the continuity of the animated series, rather than mainline DC canon – she apparently didn’t appear in DC’s main canon until 1999.
Harley Quinn is an odd case, being an animated character incorporated into regular continuity from the cartoons.
There already was a Female Joker character named “Harlequin” in the 1970s and 1980s. Duela Dent originally claimed to be the Joker’s Daughter, and her face looked pretty similar (although her origin and relationships changed many times). She never really caught on, though. (and there were three other DC “Harlequin” characters, as well – Harlequin (DC Comics) - Wikipedia )
But Harley Quinn was a completely new and different take on the concept.
Moondragon was first introduced as “Madame MacEvil.” She had a brief, but memorable run in the battles against Thanos. (In the link, bubbles are standing in for Kirby Krackle.)