It might be a parody on how some doll horses made by *certain* doll companies appear to have human breasts. http://www.youtube.com/watch?v=cY6adU5PGPg (around the middle)
It really is a melding of Komachi and Marisa. Catmel is from a comic and was a pretty famous touhou meme back in the day. You can read them by clicking the "catmel" tag. If you have the time, read the entire thing. It's absolutely hilarious. Likely my favourite touhou comic, actually.
