She was looking at his bulge and asked, "Joe let me take one wish".
"Okay but what do you want?" he asked a little worried.
"Oh common let me shock you too" she told him putting her hand into his pants.
"Okay, I wish that my lover will have one erotic wish"
"Do you still lack any faith in me I... ", he stopped her in mid sentence "I also wish that she can make a wish to change something about me"
So many options:
She has big boobs he have big dick
She wants to be a male with big dick
She wants him to be smaller
She wants to be furry
Change genders