Preheat the oven according to the cake mix package directions. Prepare and bake the cake in a 9 x 13-inch baking dish according to the package instructions.

While the cake bakes, prepare the pudding according to the package directions. Stir in ½ cup of the peanut butter until smooth. Set aside.

Place the remaining ¼ cup peanut butter in a microwave-safe bowl and heat for about 20 seconds. Stir until smooth.

Place the chocolate frosting in a separate microwave-safe bowl and heat for about 20 seconds. Stir until smooth and pourable.

Remove the cake from the oven and allow it to cool for 5 minutes.

Using the handle of a wooden spoon or a chopstick, poke holes all over the cake, spacing them about 1 inch apart.

Drizzle the melted peanut butter and chocolate frosting over the cake.

Pour the peanut butter pudding mixture over the cake and spread it evenly, gently pressing it into the holes.

Refrigerate the cake for 30 minutes to allow the filling to settle.

Spread the whipped topping evenly over the chilled cake.

Sprinkle the chopped Reese's Peanut Butter Cups and Reese's Pieces over the top.

Refrigerate for at least 30 minutes before slicing and serving.