Preheat oven to 350F. Line a 9×13-inch pan with aluminum foil and spray with cooking spray; set aside.
Make cake according to package directions (likely adding 3 eggs, water, and oil) and bake as directed.
While the cake bakes add the peanut butter to a large, microwave-safe bowl and heat to soften, about 15 to 30 seconds.
Add the sweetened condensed milk, caramel topping, and whisk to combine; set aside.
Remove cake from the oven when it’s done (probably about 23 to 28 minutes) and using the blunt end of a wooden spoon, poke holes over the surface of the cake. I didn’t count but I estimate I poked about 60 holes, evenly spaced over the surface.
Slowly pour the peanut butter and sweetened condensed milk mixture over the holes, taking your time to evenly distribute it so that all the holes receive some. Place cake in the fridge for about 10 minutes to cool slightly before adding the whipped topping so it doesn’t melt.
Remove cake from the fridge, evenly spread the whipped topping over the surface, and evenly sprinkle the peanut butter chips and peanut butter cups. Cover cake and refrigerate for at least 2 hours (overnight is best) before slicing and serving.