Now this one is one of the dumbest and weirdest things ever, but somehow it’s hot. Do not question me why, I don’t know either.
It’s basically the process of something or someone crawling up (or insterted) into a woman’s vagina, most of the times directly into the womb. The important part here, is that it is something alive that gets in there, and not just some toy. I guess something robotic would work as well… This then, of course, often comes with Cervix Penetration.