I remember this really... really disturbing pokemon fanfic that was about Pokemon that was being controlled by by a unknown force that was making them... well... do the Bow Chicka Wow Wow with their trainers! Later in the fic, I think it was shown that after a pokemon had their "way" with their trainer, the trainers turn into a gijinka, the word I'd used, version of the pokemon. Yeah...! XD I can't remember the fanfic clearly nor can I find it on FF.Net anymore, but I think Lance (That's right! Lance of Elite Four Fame!) was the one who was causing the whole hanky panky fiasco!
I didn't finish reading it nor do I want to! It's a really freaky, so I don't want to look for it again! XD