Prepare and bake cake mix according to package directions for a 9x13 inch pan. Poke holes in cake while still hot with the round handle of a wooden spoon. Make gelatin with only 1 cup of boiling water. Pour liquid gelatin over cake while hot. Cool cake completely.
Beat together whipped topping, pudding mix, milk and vanilla extract. Pour mixture over cooled cake and refrigerate until ready to serve.
