New character idea. A dragon, or similar creature that might contain a genital slit, but what's inside the slit is a complete mystery until the genitals are exposed, which can happen through arousal or curious extremities. It could be a penis. It could be a vagina. It could be both. It could be neither! Just a wrinkle that doesn't go anywhere. It could be a mass of tentacles (watch out for those, they're a bit grabby!) It could be an ovipositor!

Horse cock, dog cock, dolphin cock, lizard cock, no cock, cock snake, cock tongue, tentacle cock, tentacle clit, psuedopenis, vagina that could fit a 30' dick, tiny little pocket, toothy (oh god no D:) vagina, vagina mimic (WHY?!), triple vagina, etc. And you never know what you're going to get until the genitals are exposed! Once the genital slit closes up again? Back to the mystery slit!

It is possible to influence what might show up, making it much more likely to get what is desired at the time, but one can never truly know specifically what will appear. Except for maybe the creature with these genitals. And they'll never reveal what's going to show unless they REALLY like you ;D