Combine the lemon gelatin and boiling water in a medium bowl or large Pyrex measuring cup. Stir until the gelatin is completely dissolved. Stir in the mango nectar.
Pour one ounce into each two ounce shot glass. Any leftovers can be poured into other glasses or a small pitcher.
Place in the refrigerator and chill for about one hour. The gelatin mixture will be thick but not set up like gelatin.
When you are ready to serve, pour one ounce of orange soda into each shot glass. Use a spoon to divert the flow of orange soda. Just pour gently onto the spoon to maintain the integrity of the layers.