You think that you're good to go, but then you feel a strange sensation in the worst of places: your cock. You pull down your pants to get a better look, and are surprised to see that it's not only fully erect but also definitely longer than before. If you had to put a number on it, you'd probably say it was eight inches (though you know that your rough estimates of your own member are about as good as year-old cheese). The satisfaction at your rather large cock turns into fear as you see that it's still extending.
Terrified, you do the first thing that comes to mind and grab the sucker. Bad idea - this only stimulates it, causing the black latex forcing it's growth to start dribbling out like cum. Now, while the stuff continues to blow your penis up like a balloon from the inside, it slowly coats it on the outside. Within a minute, the stuff seems to stop pouring down as it finishes coating your trouser snake (you mutter a silent thanks to the powers that be for leaving your balls untouched), which is now a good foot and a half long as it begins to bend... sideways?
You think it might be a trick of the light, but as your appendage balloons out to around two feet you can clearly see that it's bending off to the right. And now to the left. Now down. Now it's curling up. The thing seems to be completely prehensile. Not just that, but as it expands further it seems to be taking on a familiar shape. Once it finally stops extending at about three feet, you can clearly make out what that shape is. Where your penis used to be, there is now a long black latex elephant trunk, apparently swinging about with a mind of its own.