Mix and bake cake in 13x9 pan according to package instructions. Allow the cake to cool.
Using a fork, poke holes in the top of the cake.
In a small bowl, mix together gelatin with 1 cup of boiling water until dissolved. Pour the gelatin over the cake, making sure to pour over and into the holes.
In a small bowl, mix together the French vanilla pudding mix and 1 ½ cups of milk. Allow the pudding to set for 3 minutes, then spread it overtop the cake.
Add a layer of half of the Mandarin oranges over the pudding.
Top with whipped topping and the remaining Mandarin oranges.
Cover and chill for 4 hours before serving. Keep refrigerated.
The calories shown are based on the cake being cut into 15 pieces, with 1 serving being 1 slice of cake. Since different brands of ingredients have different nutritional information, the calories shown are just an estimate.