Line a baking sheet with waxed paper; generously coat waxed paper with cooking spray. Insert 1 skewer into the top of each apple slice.
In a large heavy saucepan, melt butter over medium heat. Add marshmallows; stir until melted. Dip apples, one at a time, into warm marshmallow mixture, allowing excess to drip off. Place on prepared baking sheet and refrigerate until set.
In a microwave safe bowl, melt chocolate at 50 percent power for 1 ½ minutes. Carefully remove from microwave (bowl will be hot) and stir. Continue to heat at 50 percent power in increments of 30 seconds, stirring in between until melted and easily stirred.
Remove apples from the refrigerator and dip whole in chocolate and then coat with graham cracker crumbs. Place on baking sheet. Refrigerate until set.