Ok, start the story from the part of you lying on your stomach as she approached from behind 
Long story short, I was out one night years ago(2003), and I was yapping with this dude and his gf, they invite me over for drinks after. Get there and anyways it's a huge shared house(more to come on that lol) anyways he leaves me alone with his gf in his room and I am sitting across from her(small blonde)
I am starting to get a funny feeling that they are freaky possibly when i notice she is wearing some pretty big underwears and very tight ones to boot(she is wearing a mini skirt.
All of a sudden instict kicks in(as well as drunken bravado) and I flat out ask "No offense, but are you a dude?"
She/he responds yes. Ok well I leave it that, her bf comes back to the room with beers.
I sit and chat with them a bit but me asking that and the vibe I gave change the atmosphere, at least good for me, but this is where it gets freaky.
After the beer I make my excuse to leave, am polite and so they escort me out, everything is cool, it's about 3AM or so and sitting around the kitchen table at this point are a whole sqaggle of trannies and/or drag queens.
Luckily they were all cool and not of the rapist drag queen/tranny variety.
I meet all kinds. If I had not noticed those panties i would have hit on that tranny, she was that convincing as a chick and I would have been more disappointed than a kid rifling a cereal box for the toy once I reached down there
