Pour 1/2 cup Hawaiian Punch in the bottom of the glass, then place a small scoop of Vanilla Ice Cream in the glass, carefully pour about 1/2 cup of diet 7-Up over the ice cream. Pop the "severed finger" ice cubes out of the tray and place in the glass!! Thats it. If you don't have the finger ice cube tray just freeze the Hawaiian Punch in a regular ice cube tray this will work just fine and because you are freezing Hawaiian Punch the ice cubes won't water down the "Mocktail"!!
In medium bowl, mix powdered sugar and butter with spoon or electric mixer on low speed. Stir in vanilla and 1 tablespoon of the milk.
Gradually beat in just enough remaining milk to make frosting smooth and spreadable. If frosting is too thick, beat in more milk, a few drops at a time. If frosting becomes too thin, beat in a small amount of powdered sugar. Frosts 13x9-inch cake generously, or fills and frosts an 8- or 9-inch two-layer cake.
Heat oven to 350°F (325°F for dark or nonstick pan).
Make and bake cake using th ediet 7-Up only. Bake according to direcitons on back of box for cupcakes. Pierce cooled cupcakes about 3-5 times on the top of cupcake with a fork. In small bowl, stir gelatin and boiling Hawaiian Punch until smooth;gelatin is disolved let cool until about room temperature . Carefully spoon teaspoonfuls of gelatin over cupcake one at a time. Let gelatin set up and then frost cupcakes with buttercream frosting. Carfully push 2 red M&M's into frosting and drizzle with to lines of fake blood!