Measure out 1 ½ cups marshmallows and set aside to mix in later. Add the rest of the marshmallows to the melted butter, stirring constantly, until the mixture is totally melted and smooth.

Remove the pot from the heat and stir in the vanilla extract and salt.

Fold in the cereal, remaining mini marshmallows, mini pretzel twists, M&M’s, candy corn, and sprinkles until combined and evenly distributed.

Spread the Rice Krispies mixture evenly into the prepared baking pan using a silicone spatula. Do not press it down firmly as you will end up with hard treats.

If using, melt the candy melts in a piping bag in the microwave on the low or defrost setting until fully melted. Massage the bag every 30 seconds to ensure even heating.

Allow the candy melt mixture to cool for 5 minutes before snipping a small piece off the tip and drizzling it over the prepared treats. Immediately top with additional toppings such as more M&M’s, pretzels, candy corn, and sprinkles if desired.

Allow the treats to cool on the counter for 30 minutes to 1 hour before cutting into squares.