Why's our Tux squished?
He's short and fat, but he's not supposed to be that short and fat. The image's x-y ratio was altered.
This seems to happen all over Kbin (image previews) if the image is not square. Though in this case there doesn't seem to be a better version saved.
Could produce an image with some padding to avoid the problem, but the general fix is probably to file an issue on it until kbin gets a patch to permit proportional thumbnails.