I seem to remember, somewhere in the distant mists of the Internet Time past (distinct from, say, Valve Time), some sort of diatribe going around the English-language anime blog community like some sort of strangely-contagious cold. I think it had something to do with K-On at the time, as a catalyst for an issue that had been bubbling away for some time. I posted something in reaction based on what was being argued at face value, because I was still not sure what I thought about the general case yet.
I'm still not sure, but I might have ascended to a higher level of ignorance. I think. Maybe.
The argument put forth is that a character who is, shall we say, not entirely quick on the uptake when it comes to mental gymnastics should not be popular. The term used was "retarded moe", which strikes me as an odd effect of semantics: by using what has become an insult in many juvenile mudslinging matches, coupled with the probably-oversimplified idea of moe commonly held to be the entire territory itself (instead of merely a guide map), the issue has become equally oversimplified, and boiled down to its extremes. It's easier to attack the edges of the graph, even if they turn out to be strawmen.
I've noticed that this "retardedness", and I am willing to experiment with other terms to find one that fits better, comes in a variety of flavours, and it's not really clear where one begins and ends, as well as the differing subsets and intersections thereof. Off the top of my head, there is the one which seems to be the primary target, exemplified (at least in recent memory) as Fuuko from Clannad: clumsy and bad at schoolwork, and not exactly overflowing with common sense. Clumsy Stupid characters mess up a lot, but always in an adorable manner, and the viewer is supposedly compelled to help them out if only to keep them from hurting themselves. Not because they're liable to poke pencils into their ears, but because they don't give up, and they'll keep doing whatever it is they do, no matter how many times they fail.
Then there is the Straightforward Stupid, as seen (again in recent memory) with… well, not Negi, but more his father Nagi, in Negima. The idea of Nagi's special brand of idiocy is discusses at some length in the manga: it's not so much plain stupidity as a sort of stubborn bloody-mindedness, a feeling that everything can be dealt with if you have More Power, or More Love, or More Spiral Energy, or whatever. A direct, straightforward rush, and a refusal to worry about the little details beforehand, although it should be noted that they don't completely ignore them either; they just deal with it as it comes. This is the Stupidity of the typical shounen action hero protagonist. I'm a little iffy about this one, because there's a hint of anti-intellectualism involved: why bother with thinking intelligently when it's shown to be less effective than blasting through everything at loud volumes?
There's the Cheerful Stupid, again shown in recent works with Recette from Recettear. The "well, I don't know what's going on, but everyone should get along" sort. The ones who have their own invincible magic of Zettai Daijoubu. There's an unrelenting, unceasing cheer which, assuming the setting is light enough to allow it, infects everyone else and brings them around to the Cheerful Stupid character's viewpoint, full of cheer and hope. If they worry about things, it will be the little details that everyone else sees as unimportant. Maybe they believe that the big problems would be solved "somehow", through sheer determination, or they know that worrying about it isn't going to make things any better. This overlaps to a certain degree with the Clumsy Stupid: they keep trying, because they believe that in the end, they'll succeed.
We also have the Prideful Stupid, which was what prompted this rambling post. Anime-wise, we see it with Ika Musume in her titular anime, but I was pondering this while reading various 4koma doujins of Cirno from the Touhou-verse. This brand of Stupidity has a lot of links to the Straightforward version, but it also has some effect for the Cheerful Stupid at times. The idea is that the Prideful Stupid character is the best person for the job, and possibly the best person period. The leadership position should fall to them naturally, even though they might not actually know what to do; they just think they're qualified, and don't bother them about the details. Ika Musume wants to take over the world, even though she has no idea what the world is like. Cirno says she's the strongest, even though she's at the low-tier of power objectively.
There are plenty more varieties, of course (for example, the Spacy Stupid, as seen in the later portrayals of Osaka-san in Azumanga Daioh). And this doesn't always have to do with anime, or even moe, but that's outside the scope of this blog. Well, to be honest, it's more of a raised eyebrow at the possibility of this post being even longer than it already is.
I suspect some of it is indeed due to the Stupid Person being female, and a cute anime girl at that. We forgive a lot of things when it's presented with eye candy. This effect also applies to small children of either gender, assuming you don't actively dislike small children of either gender.
In fact, it's often because this trait of Stupidity resembles that of young children that there's an unexpected appeal. Here, the Stupidity is transformed into Innocence, or perhaps Naivete. Not knowing the ways of the world, and not caring, as long as they have fun. Coming up with even more bizarre ways of dealing with the little inconveniences and problems of life that we, burdened with Common Sense and Practicality, might not have the imagination for.
This might be why we may be particularly affected by the thought of these young characters grown up, and remembering the stupid fun things they did in childhood. The ephemerality of this innocence is far more effective than when the characters are forever young and Stupid. Someday, Calvin will grow up, and we wonder if he will still remember Hobbes.
And when I look at pictures of Cirno, the ones which I love most are those with the rest of Team 9, portrayed as Cirno's gang of friends. Because here and now, in this frozen instant of time, she is indeed the strongest.