Combine the salted butter, peanut butter, and chocolate chips in a medium glass bowl or microwave-safe bowl. Microwave for 45 seconds, stir. Microwave for another 20 seconds or until melted. Stir to combine. Stir in the vanilla extract.
In a separate large bowl, add the rice Chex cereal. Pour the melted chocolate mixture over the cereal and gently stir to coat the cereal completely.
Add half the cereal mixture into a large gallon-sized Ziplock bag, and add half of the powdered sugar. Shake to cover the cereal completely with the powdered sugar. Pour into a large bowl. Repeat again with remaining cereal mixture and powdered sugar. Once coated, place into the large bowl.
Gently fold in the candy corn, candy corn pumpkins, peanut butter mini pumpkins, and Reese’s pieces, and sprinkles, if using.
Line a large baking sheet with parchment paper. Spread the muddy buddies out onto the baking sheet in one layer. Allow to rest for about 30 minutes before serving. Enjoy!