[quote name="Ymono37"]
I still don't get tentacle-rape porn.[/quote]
I thought I shared that with this group...ahh well, here it goes.
In Japan, Anime isn't pigeonholed like animation here was--where cartoons were considered "for kids only". Over there, it has pretty much been as diverse as live action films--with stuff like Hello Kitty all the way up to Hentai (pervert) stuff.
So, back I believe in the late 60's/early 70's, when the Anime industry was beginning to take off (Speed Racer, Astro Boy, etc.), there was a movement to create Hentai as a method to bypass the laws stating that genitals cannot be shown in japanese films. Well, from what I undersood, and again, this i just heard--it may not be true, they let the genital issue slide, but kept ome regulation saying that even in Anime, you could not show the act of copulation between a depictio of a human Male and a human Female. So, what one intrepid artist did was substitute human male penis penetration to demon or alien tentacle penetration, which was supposed to be a lot worse and yet somehow, that was allowed to be shown.
It might have been the classic "Urotsukidoji", but don't quote me on that.
Anyhow, it caught on. Thus perpetuating the "Japan: providing 70% of the world's most fucked-up shit since 1960" saying.