Line a baking dish with parchment paper and set aside.

In a large pot, melt butter. Once butter is melted, stir in mini-marshmallows.

Stir the butter and marshmallow mixture continuously until incorporated and marshmallows are fully melted.

Remove from the stove and quickly stir in cereal, until all pieces are coated with marshmallow mixture.

Transfer mixture to the lined baking dish and using an additional piece of parchment paper, lightly press the crispy treats into the dish.

Let the treats cool for 3 minutes and then add on sprinkles, candy corn, and pieces of the dark chocolate bar and crushed pretzels.

Press the toppings into the crispy treat surface to get them to stick on top, and let the tray rest for 1 hour before cutting into a dozen square pieces.