You will need:
A cake mix (and the ingredients that your mix needs such as eggs and oil)
a small box of Jello
Bake your cake in a 9x13 pan according to the box directions. Allow to cool for at least 20 minutes. Poke holes in the cake with the fork, across the whole cake.
Add 1 cup of boiling water to the Jello and stir until dissolved. Stir in 1/2 cup of cold water. Pour the Jello mixture over the the entire cake. Refrigerate the cake for 3 hours, until the Jello is set. Top with whipped topping. You can use any Jello flavor you want, I personally used Strawberry Jello and yellow cake mix.
The delicious dessert requires some prep time, but comes together really easy and it is a fun crowd pleaser.