Preheat oven to 350 degrees. Spray 60 mini muffin cups. Make cake batter as directed on box. Divide batter among 5 small bowls, about 3/4 cup each. Make 5 different colors of batter by adding 1/4 teaspoon food color to each bowl. Blend well.
Fill each muffin cup with 1 level measuring tablespoon of batter, making 12 cupcakes of each color.
Bake 10-12 minutes or until toothpick inserted into center comes out clean. Cool 5 minutes. Remove from pan. Cool completely, about 10 minutes.
In a large bowl, beat marshmallow cream and butter with electric mixer on medium speed until blended. Beat in powdered sugar until fluffy. Divide frosting among 5 bowls, about 1/3 cup each. Using the same 5 colors, lightly tint frosting in each bowl to match the cupcake colors.
Assemble each popper using 2 mini cupcakes. Cut tops off each cupcake horizontally (save bottoms for another use). Spread or pipe about 1 tablespoon frosting on cut side of 1 cupcake top. Form a sandwich by placing cut side of second cupcake top on frosting. Press lightly. Repeat with remaining cupcake tops. Store loosely covered.