Bake cake in a 9x13 pan, according to package instructions, let cool & cut into 1" squares.

Make instant pudding according to the directions, let sit in refrigerator for approx. 15 minutes and then fold 1 tub of cool whip in, return to fridge until you're ready to assemble.

Chop candy into chunks beforehand, stick in fridge if it's humid or too warm so it won't clump together, until you're ready to use it.