1. Cut the oranges in half from top to bottom and spoon the fruit from each half, leaving the peel intact. Prepare the gelatin according to the package directions, then pour it into the peel halves, adding fruit pieces if desired.
2. Set the halves into ramekins or a muffin tin to keep them from tipping and carefully place them in the refrigerator. Let the gelatin set according to the package directions.
3. Once they're ready, remove the orange halves from the refrigerator, cut them into wedges, and serve. Tip: For a colorful twist, try using other citrus fruits and gelatin flavors, such as grapefruit, lemon, and lime.