The first one was MANtis, which kind of sort of made sense since it's a play on words and his posture is that of a preying mantis. But then reapersun made more, and now they are like one of those annoying memes everybody and their brother keeps regurgitating over and over till it makes no sense and just isn't funny any more.
They creep me out too, especially all the early RIG ones. It'd be less odd if they actually had similar proportions to actual avatars. I think the only ones slightly like that are the Celebrity Date ones.
I also remember a halloween event involving a ghost who posed similarly to the MAN characters...as well as the king one, or whatever. Was it last year's halloween? Or the year before? Well anyway, that's when they all just started to appear at once.