Say, "Call me Daddy."

I grin. This not being nearly the first time I've heard that request, I don't miss a bit and say, "Okay. What do you want to do with me, Daddy?"

I put my hand on your arm and explain, "You'd be surprised how many guys want me to call them that. I've got a few changes of clothes in my bag for role playing. If you want to roleplay a little daddy-daughter scenario, I can provide that for you." I raise my eyebrow and let you think about it for a second before adding, "Or did you just want me to call you daddy?"