I'm not really a data guy, so this is going to be a pretty superficial analysis.
Including the Companion and Grog characters for Ars Magica and the Villain character for Princess of the Universe, I statted out 34 characters for this project. I was consciously trying for variety: not only of rules systems and genres, but also of types (bricks, brains, swashbucklers, faces, sneaks, etc.) and of demographics (species, ages, ethnicities, genders). I think it's fair to say I could have followed through more effectively on diversity.
When I'm actually playing, I'm inclined more toward faces, brains, and swashbucklers than I am to sneaks or bricks, and probably least of all to sharpshooters and petmasters. In addition, these days I prefer to play clear-cut heroes instead of morally ambigious or even villainous characters; I don't know how much of that is a reaction to the times we live in, but I'd guess a fair amount of it, though I wouldn't disregard my age as a factor either. In tabletop RPGs I tend to play cross-gender characters about 40-50% off the time, though as far as I know they've always been cisgender (and generally heterosexual, though I've never been particularly interested in my characters' sexuality so I haven't explored those questions much). And where human ethnicity has been relevant, my characters have usually defaulted to white. (For reference, I'm a cishet, middle-class white guy.)
I went into this project not expecting to play any of the characters I generated, which in theory should have given me some extra leeway to explore character ideas I might not be super comfortable playing in a live group. In practice, it didn't really turn out that way, and though the time pressure built into the project may have played some role in those decisions I doubt it was a significant factor.
So let's break some of this down. Out of 34 characters,
15 were male (and probably cisgender)
13 were female (and also probably cisgender, except one case which was explicitly cisgender)
6 were not gendered: two of these were explicitly nonbinary humans (Psi World, the hero for Princess of the Universe), one kept their gender shrouded in mystery (Ars Magica), one was a member of a nonbinary alien species (Teens in Space), one I left ungendered because I didn't see any reason to give them a gender (the villain for Princess of the Universe) and one was a crayfish, who I suppose probably had a gender, but it was completely irrelevant for the game's and my purposes (Creeks and Crawdads).
31 of 34 characters were human, including characters with super-powers but no explicit non-human ancestry and human brains in non-standard bodies. One of the remaining three was an extraterrestrial in an SF setting (Teens in Space); the other two were animals in animal-based settings (Bunnies & Burrows and Creeks & Crawdads). The absence of fantasy non-humans such as elves or goblins is primarily a result of the games I chose, most of which didn't have nonhuman options, though I certainly bypassed non-human options in the supers systems, Timewatch, Torg, and the one D&D-alike on my list (Warhamster Dungeon Adventure).
More often than not, the human characters' ethnicities tended to default to white. (I'm including characters whose ethnicity I didn't establish during character creation, since that's how I'm inclined to roll when I'm not thinking about it.) Most of the exceptions involved contemporary or historical(ish) non-European settings: either built into the game (such as Legends of the Wulin, Coyote and Crow, or Bushido), or posited for a generic rules set (Mini Six and Wushu, both of which I set in contemporary East Asia). Altogether, 11 of the 31 human characters were explicitly or implicitly persons of color (and that doesn't include the one explicitly Jewish character, who is overall coded white):
East Asian: Mini Six, Legends of the Wulin, Wushu, Bushido, OVA
African-American: Hollow Earth Expedition
South Asian: Lancer
Arab: Torg
Latino/a: ICONS, Spookshow
Explicitly Mixed: Universe
Native American: Coyote & Crow
That lineup smacks of tokenism, and I'd like to do better in future attempts (though also without straying into stereotype or appropriation).
Agewise, characters ranged from teenagers (Hellcats & Hockeysticks, Teens in Space) to late middle age (Hollow Earth Expedition), though the vast majority of them were adults in their prime (i.e., between 20 and 40, or the species equivalent). I really didn't give age a lot of consideration when creating characters (both teenagers were created for games where PCs are expected to be teenagers), and it shows. (I also ignored disability almost entirely, with only one character having a physical or mental disability of any kind.)
As far as character types go, I seem to have achieved a pretty broad spread while still indulging some of my preferences for smart and/or agile heroes. The taxonomy used below is a very rough guide, and some characters will appear in more than one group.
Big Hitters: Big Lu (Legends of the Wulin), Tom Hayward (Clockwork & Chivalry), Harmony (The Well), Gretchen Hastings (Hellcats & Hockeysticks), Boomblasto (Princess of the Universe)
Detectives & Investigators: Taga (Coyote & Crow), Shiro Tanaka (Mini Six), Benjamin da Silva (Colonial Gothic), Veronica Garcia (Spookshow), Dr. Daniels (Timewatch), Brad Milgram (Unknown Armies)
Faces & Schemers: Rinaldo of Piacenza (Ars Magica), Burrberry (Bunnies & Burrows), Cornelia Vane (Soap), Taga (Coyote & Crow), Shiro Tanaka (Mini Six)
Healers: Dr. Charles Sumner Thornton (HEX), Benjamin da Silva (Colonial Gothic), Dr. Daniels (Timewatch)
Petmasters: Alisha Shah (Lancer)
Pilots & Drivers: The Falcon (Torg), Alisha Shah (Lancer), Yuka Asagami (OVA)
Scientists & Gadgeteers: Bio-Battery (ICONS), Haruko Kenyatta (Universe), Veebolitt (Teens in Space), Mechanis (Princess of the Universe), Splitter (Creeks & Crawdads), Dr. Daniels (Timewatch), Brad Milgram (Unknown Armies), Doc Pliable (Capes)
Swashbucklers & Acrobats: The Falcon (Torg), Zara the Cutlass (Barbarians of Lemuria), Sabine the Cat (Jaws of the Six Serpents), Doc Pliable (Capes), Martin Yim Kwok-kwan (Wushu)
Sharpshooters: Gianna (Ars Magica), Tom Hayward (Clockwork and Chivalry)
Wizards: Matsumoto Yaemon (Bushido), Opacus (Ars Magica)
Sneaks: Kelvin the Uncatchable (Warhamster), Jer Landon (Psi World), Veronica Garcia (Spookshow)
There
are two characters who, due to the way their game systems work, didn't
really fit into my typology: Maria (My Life with Master) and Charles
VIII of France (Statecraft). The role that a Minon plays in My Life With
Master and that a head of state plays in Statecraft don't easily map on
to traditional RPG character categories, though I suppose that if I had
to force it I could call Maria a Sneak and Charles a Schemer.
I've never been much for playing sharpshooter characters, and I didn't think to make the effort to include them, so it doesn't surprise me much to see only a couple of characters who fit that category. Likewise for petmasters; running multiple subordinate characters isn't usually my bag, but I liked the drone thing for Lancer so I went for it. With wizards, I think the main reason there's only two in my list is that a) engaging with magic systems adds time and complexity to character creation, so I tended to bypass it; and b) in most games it tends to require a significant enough investment of resources that your character doesn't have a lot left for other skills (e.g., I wanted to make my Colonial Gothic character a natural philosopher who also did magic, but I felt I couldn't split the difference without making the character medicore at both). Also, when faced with a sword & sorcery setting I tend to swing hard towards swashbucklers, and that's exactly what I created for Jaws of the Six Serpents and Barbarians of Lemuria. I've never been averse to playing healers, though, so I'm a little surprised to see that I only made three (and that's counting Dr. Daniels' Reality Anchor skill as a healing ability, which I guess it is but he doesn't do physical treatment so maybe he should only get half credit).
So I don't know how to sum all that up, except that just creating a new character for a different and unfamiliar system every day took me far enough out of my comfort zone that I didn't put a lot of effort into pushing on other limits. (Also, I wanted to be respectful when addressing the experiences of groups that I don't belong to, and that requires time and energy that I didn't always have.) It's another argument for using either fewer systems (and so creating groups of characters), more familiar systems, simpler systems, or some combination of the three for next year's go at the challenge.
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While I'm here, I'd also like to talk a little about engagement. Most of the traffic to this blog, I'm pretty sure, has come from members of the RPGNet forums (where I've been posting the characters and post links in the Character Creation Challenge thread in the Tabletop Roleplaying forum), from my own gaming groups, and from my wife. I have no idea what has made certain posts more interesting than others, but there are definitely a few that got markedly more views than others. The Soap character from day 7, at 20 views, is currently the highest performer, followed by day 1's Unknown Armies character (17) and day 31's Universe (11, but I gave it some extra plugging). About half of the remaining character posts got as 5 or fewer views, but I think that may exclude all the people who just read whatever was on the front page without clicking to a particular post, so I can't say anything for sure.
But I'd sure be interested to find out why it seems so many more people wanted to read about my Soap character than anything else.