It is an image compositing error (there are several throughout the game). Attached is a quick fix for it (I spent less than a minute testing locally and it seemed to work fine).
Unzip into your game folder (where the .exe is), so that the .rpy file ends up in the top level of the game folder. That should fix the problem for you.
Wonder if we'll change cyborg that or if we'll see some reverse bestiality where we screw the animal. Just take Beast girl to pound town while they're in a different shape, that or if they'll bring the youth potions to this game or something.