Bake cupcakes according to directions on the box (or bake a batch of your favorite homemade cupcakes)
Make frosting. Beat softened butter and vanilla until smooth using a hand mixer or stand mixer. Slowly add sugar to butter while mixing. Once butter and sugar are combined, add one teaspoon of milk at a time until desired consistency is reached.
Make bunny ears. Cut 24 marshmallows on a diagonal with scissors. Dip the cut side in pink sugar sprinkles.
Once cupcakes are cooled, frost cupcakes. Top frosted cupcakes with coconut shreds (optional) and place 2 ears in each cupcake. (If you choose not to use coconut shreds, simply place marshmallow ears directly into the frosting).