"Three!"
You both throw your hands out and the outcome is fast. While your girlfriend had choosen paper, you had wisely countered with scissors. "Ha ha, I've won, scissors beats paper" you declare as you're win the game.
"*sign*, Yeah... you win, and I lost the game so you can change me whatever you want, but you better not to change me into something stupid, alright?" your girlfriend warns.
"Hehe, don't worry, I would never think about wasting this chance just to make you angry. Besides, why would I do that when I can make you into whatever I desire. And on top of that, you still have a chance to change me when I change you back." you finish with a smug look on your face.
"Hmmm, I guess you're right. Why waste a great chance, right? So who or what will I be for you, huh?" she questions.
"Well" you start,"I guess I will change you into..."