In a large bowl, mix together cake mix, eggs, butter, and milk. Spread in the bottom of a greased 9x13" glass dish.
Spoon one of the tubs of marshmallow creme over the cake mix. With a spoon, gently swirl the two together. You don't want to mix; you should still see separate swirls of marshmallow and cake mix. Make sure you swirl the mixture to the end of the pan.
Sprinkle marshmallows over the top of the swirl mixture and gently press in. Repeat with half of the graham crackers and the chocolate bar pieces.
Bake mixture at 350 degrees for 35-40 minutes, until the center of the cake is not jiggly. Let cool for 15-20 minutes.
While cake is cooling, mix together frosting and the other tub of marshmallow creme. Frost cake with this mixture. Crush remaining graham cracker into fine crumbs and sprinkle over the top of the frosting.
Serve warm. Enjoy!