how (robot) babies are made
When one robot loves another robot very much.... human reproduction re-told with robots. From the classic "How Your Body Works" (Usborne Publishing, originally from 1975 though I only have the 1995 edition), p38-39.
I think it's an interesting example mechanical metaphors in educational materials about the human body (blogged).
There is also an analysis to be made of this in terms of visual narrative (i.e. way movement from left to right hand side of the page is signaled), especially when it comes to the, um arrow-like aspect of parts of the blue robot's body. But that's another story.
I also like how the robot before penetration is blatenty grinning, but gets all serious in the right-hand image. Really, look at the slight angle on his mouth.