Hehe well my wife got mad at me for #3, so i will point out I was kidding. I dont endorse cheating on anyone. To make up for it, heres another #3: Good communication. Be honest and open about your fantasy, and if she truly loves you, she will probably at least be willing to play with you in some way in that regard. Beyond that its just a matter of whether she enjoys it as much as you do.

Good luck!