…my dad.”
"Wait, your dad?" Your girlfriend asks as she's confused. "Wait a second, I didn’t know you had a dad, hun. I thought you had your mom only."
There wasn't much time to ponder this though as your girlfriends changes had already begun. Since you both were now at the same age of 16, your dad was about 45, and your girlfriend's age seemed to be changing too. While she grew taller than her 5'2" height, her hair was shortening. Her hair, which was shoulder length and light blonde, was now shrinking above her head, turning a deep brown. While this was going on, all her clothes seem to have vanished to allow her to keep growing in all areas. Next are her breasts, which deflate from a nice C cup, you didn't realize your dad was so big. Along with her chest, her skin seemed to darken a bit from a tan, and all excess hair on her arms, crotch, & body suddenly appearing. Her whole body had become more toned, as your dad worked out a little more than your girlfriend had. Her face and voice both seem to contort and reform back to that of your father's image.
Finally, her crouch begins to grow a penis and becomes larger in size.
"Ohh... my god, something is growing between my thighs," your transformed girlfriend responds with her... or rather his new old manly voice as s/he's holding his crotch. The transformation has been completed.
“Wow, I look & sound different.” s/he said in a deep voice.
“Well, as you can see.” you begin,"You could say we all have our own dirty fantasy or kinky that we might never get to try out. However, here we can try just about anything and nothing bad will come from it, because no matter who we change into, it's still just me and you.” “We can have fun with each other, …dad” you say.
“OK, then. If that’s what you want, then you got it.” s/he said.
S/he wraps her arms around you and kisses you deeply. The whole experience is sureal as not only are you kissing your dad's body, but your girlfriend had added your dad's nickname for you right before s/he did it.