Preheat oven to 350°F. Prepare cake mix as directed on package, adding cocoa powder, red food color and vanilla. Pour batter into greased 13x9-inch baking dish.
Bake 30 to 40 minutes or until toothpick inserted in center comes out clean. Cool completely in pan.
Poke large holes all over cake using the end of a wooden spoon. After holes are made, mix milk, raspberry extract and neon blue and neon purple food colors in large bowl. Add pudding mix; stir just until mixture begins to thicken. Immediately pour pudding over cake, filling the holes.
Frost cake with whipped topping. Refrigerate at least 1 hour or until ready to serve. Sprinkle each serving with Pop Rocks®.
For best results, do not sprinkle entire cake with Pop Rocks®. (The candy will melt as it sits on top of the whipped topping.)