Preheat oven to 350 degrees. Prepare cake mix and bake in 24 paper-lined muffin cups, as directed on package. Cool only 30 minutes. (Cupcakes need to still be warm to fill.)
Pour milk into a medium bowl. Add dry pudding mix. Beat with a wire whisk 2 minutes or until well blended. Add peanut butter; beat well. Spoon into a small freezer resealable plastic bag or pastry bag; seal bag. (If using a plastic bag, snip off one of the corners from bottom of bag.) Insert tip of bag into each cupcake; pipe in about 1 Tablespoon of the filling.
Microwave whipped topping and chocolate in a small microwaveable bowl on HIGH 1 1/2 minutes or until chocolate is completely melted and mixture is well blended, stirring after 1 minute. Dip the top of each cupcake into glaze. Sprinkle evenly with peanuts. Store in refrigerator.