Prepare cake batter according to package directions. Fill 24 paper-lined muffin cups two-thirds full. Bake at 350° for 21-26 minutes or until a toothpick comes out clean. Cool for 10 minutes before removing from pans to wire racks. Cool completely.
Tint 1/4 cup vanilla frosting pink; set aside. With remaining white frosting, create a white face-shaped stripe down the center of each cupcake. Fill in the unfrosted portions with chocolate frosting.
Attach chocolate chips for eyes, miniature chips for noses and marshmallow halves for ears. With reserved pink frosting, create mouths and fill in ears.