At first, I thought this seemed quite odd... however it appears to be not nearly as odd as I would have expected. I searched Mrs. Claus images expecting to find this:
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But what I found was that more than half of the pictures looked more like this (and this was by far not the raciest image that showed up on the first page):
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There was no such trend with Santa, as a search of his name showed only Tim Allen and this kind of figure:
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So, christmas characters are not sexualized equally. Santa is an old man with a white beard that is shown half the time with a similarly aged woman with white hair, and the other half the time with a half dressed model young enough to be his granddaughter (and I don't mean because he lives forever). To make this even creepier, often this model is further infantalized wearing pig tails or, in this case, holding a lollipop that is often associated with very young children.
They do live in the North Pole, do they not? Is Mrs. Claus not allowed to wear warm clothing in that kind of environment, or is it so essential that women keep their bodies on display all the time that we ignore that part of this story. And stiletto heels are great for walking on ice and through deep snow. Very practical.