Bake your cake in a 9 X 13 pan according to directions and allow to cool to room temperature.
Once the cake is room temperature, poke holes all around the cake. I use the blunt end of a wooden skewer.
In a medium bowl, carefully mix 1 cup of boiling water with Jello mix until completely dissolved.
Pour jello over cake and place cake in the refrigerator.
While cake is cooling, mix pudding mix with 1 cup of milk and juice from Mandarin oranges until well blended.
Fold Mandarin oranges and whipped topping into the pudding mixture until blended well.
Remove cooled cake from the refrigerator and ice with pudding mixture. Serve cold and enjoy!