Preheat oven to 350ºF and coat a 13×9 baking dish with non-stick cooking spray
Combine cake mix, eggs, milk, and oil until smooth.
Spread evenly into the baking dish, and bake for about 25 minutes or until a toothpick inserted in the center comes out clean.
Remove and allow the cake to cool for 15 minutes.
Combine lime gelatin and boiling water and stir for about 2-3 minutes until dissolved.
Stir in the cold water.
Using the end of a wooden spoon or tines of a fork, poke holes into the cake about every ½ inch on the entire cake
Carefully pour lime Jello over the cake making sure to pour the gelatin into the holes.
Place in refrigerator for at least 3 hours to allow the Jello to set up.
To frost, combine the thawed whipped topping with the vanilla pudding mix and stir until smooth.
Spread evenly over the cake and decorate with sprinkles of choice.
Store in the refrigerator.
Notes
Swap out the lime gelatin for any flavor you want. Decorate with coordinating sprinkles or fruit. Store in the refrigerator - the gelatin will cause the cake to get soggy otherwise.