It's an artifact of the free-wheeling gaming environment of the time that they felt these articles could be published at all. In today's far more sociopathic copyright/IP regime, it certainly couldn't be done. (In issue #37 Schick & Moldvay wrote that the one thing they'll be scrupulously avoiding will be the Ring Trilogy characters, because "the Tolkien estate is known to be fanatically paranoid about the slightest possible infringement of rights (whether real or imagined)".)
Below you'll see a complete list of characters included over the run of the series, including original literary creator, name of the character, and any class levels identified for them, presented in the same order as the original articles. (There are a very small number of cases, maybe 1-2 apiece, where the AD&D subclasses of ranger, paladin, or assassin were used; for simplicity, I've lumped those in with the major class types.)
Interesting -- but I probably wouldn't do this if I didn't have a D&D game-design axe to grind. Consider this list of forty-two characters, statted up in D&D terms, to be a sample of the overall genre of pulp fantasy and mythology. Here's two major observations that I'd like to make:
(1) Multiclassing is essential. More than a quarter of these characters are multiclassed (12/42 = 29%). The authors frequently found that, in simulating these characters in game terms, they had to mix-and-match abilities from different D&D classes. In almost every case the level ratios are different, showing that it's reasonable in the genre to have a lot of one archetypal class, a little bit of another class, etc.
This is part of the reason why I'm a little dumbfounded at how many people are willing to accept the Holmes/BXCMI-style abandonment of multiclassing (and the even heavier restriction of race-as-class). Clearly even the AD&D regulations on the practice were unreasonable, as the authors found it necessary to freely break or bend those rules. A free mix-and-match multiclassing rule, as suggested by the Original D&D rules, turns out to be necessary for a wide array of classic pulp character types.
(2) Clerics are almost nonexistent. Cleric-like characters appear only 3 times on the list above (and in each case, as the smallest part of some multiclass combination). Thief-like abilities, however, are found almost three times more frequently (8 characters) -- nearly as often as are magic-using wizards (10). In fact, the cleric class is so nigh-useless for this particular exercise, that they barely outnumber even the DMG Sage type for the authors' purposes here (Sage abilities are noted in the class information for both Medea and Professor Challenger).
As I've said on numerous occasions, it is the cleric class which makes the least overall sense in the context of pulp fantasy, and is the most fundamentally troubling class to be included in Original D&D. Among other multifarious reasons, the armored, adventuring, miraculous man-of-Catholic-faith is simply not a type you see very much in the roots of the genre, if at all. The inclusion really sticks out like a sore thumb in OD&D.
Okay, so having made my major points, here's some miscellaneous footnotes:
- There is some difficulty in tracking down these articles. In the Dragon "Ultimate Article Index" (August 1986), they are entirely missing -- perhaps the editors of that time were paranoid about IP infringement? Also, in the Dragon CD archive, the article in issue #61 failed to appear, and was added to the table above later (strangely appears under a different title in that archive).
- Issue #37 has a "Giants in the Earth" article with no characters included; it presents motivations, theory, and rationale behind the levels, powers, etc., used in the series. Issue #46 likewise has an article under the same header that is just a call for further articles, and a demonstration stat-block template.
- In issue #30, Gary Gygax writes a cautionary note that some of these levels may be too high, singling out in particular Kane (who indeed has the highest total levels of anyone in the list above): "I must point out that the Schick-Moldvay series 'Giants In The Earth' tends to rate the figures too high, making them more like gods than 'heroes.' Cugel is okay... but Kane is too powerful! A 30th-level Fighter/20-level Magic-User/14th-level assassin? Come on, fellows! Would you believe a 20th-level Fighter/16th-level Magic User/12th-level Assassin?"
- Much much later, in 1998, there was one additional article that used the "Giants in the Earth" banner; but this was part of a cross-promotional effort with Greg Keyes and his then-current "Black God/Waterborn" series (Keyes authored both the novels and the game writeup), using much different late-2E classes and statistics, and so is not included above.
- If you're interested in other writeups of classic literary figures from a time when such things were possible, you might also consider: OD&D Sup-IV Gods, Demigods & Heroes (including the worlds of Conan and Elric), the 1st-printing of AD&D Deities & Demigods (with the mythos for King Arthur, Cthulhu, Elric, and Fafhrd/Gray Mouser), and Gygax's lengthy Conan dossier in Dragon #36 (including his evolving abilities and fighter/thief levels from age 15 to 70, as well as a roster of special abilities which later formed the basis for the Barbarian class.)
Edit: Thanks to reader J.T. for the addition in issue #61.