Place Cool Whip in refrigerator to soften. Prepare cake as directed on box. As cake is cooling, dissolve the gelatin in boiling water as directed on package. (Do not add the cold water).
With the handle of a wooden spoon, poke holes in the cake approximately 1" apart over the entire cake. Pour the Jell-O gelatin into the holes in the cake. A small funnel works great for filling the holes.
Place cake in refrigerator approximately 3 hours to set Jell-O. After Jell-O is set, spread softened Cool Whip onto cake.