Heat the oven to 350°F and line two 12-cup muffin pans with paper liners. Prepare the chocolate cake mix with the water, vegetable oil, and eggs according to the package directions, usually beating for about 2 minutes.

Divide the batter evenly among the 24 liners, filling each about two-thirds full. Bake for 18–23 minutes, until the tops spring back lightly and a toothpick inserted into the cake portion comes out clean.

Cool the cupcakes in the pans for about 5 minutes, then transfer them to a wire rack and cool completely. Cut a small cone from the center of each cupcake, reserving the cake pieces.

Spoon approximately 1 teaspoon of hot-fudge topping into each cupcake cavity. Replace the reserved cake piece over the filling, pressing gently so the top sits level.

Frost or pipe the thawed whipped topping over each cupcake. Warm the remaining hot-fudge topping gently until it is pourable, then drizzle it over the cupcakes.

Finish each cupcake with chopped roasted peanuts, chocolate or rainbow sprinkles, and one drained, patted-dry maraschino cherry. For cleaner decorating, chill the filled cupcakes for 10–15 minutes before adding the whipped topping and drizzle.