Spread some vanilla frosting on a plate. Put some blue and red popping candy in a shallow bowl. Dip the rims of 2 glasses in the frosting and then in the popping candy. Set aside.
In a blender, combine the blue cotton candy, 1 pint of the ice cream, 1/4 cup of the milk and 1/2 teaspoon of the vanilla. Blend until smooth. Transfer to a pitcher and rinse out the blender. Repeat with the pink cotton candy and the remaining 1 pint ice cream, 1/4 cup milk and 1/2 teaspoon vanilla. Fill each glass with the milkshakes, pouring in both colored shakes at the same time so the glass is half pink and half blue. Top each with some blue and pink cotton candy, a swirl lollipop and a rock candy lollipop. Add straws and drink immediately.