Prepare and bake marble cake as directed on box. Poke holes in cooled cake with a fork. Dissolve strawberry gelatin in 1 cup boiling water. Pour gelatin over cake, and refrigerate for 2 1/2 hours. Combine whipped topping, vanilla pudding, milk, and vanilla in mixing bowl. Beat with electric mixer on high speed for 3 to 5 minutes, until frosting is thick enough for spreading. Frost cake, and serve. Store any leftovers in the refrigerator. Decorating suggestion: Top with sliced strawberries, arranging slices in circles with berry bottoms pointing out to form star patterns.