Combine the Peanut Butter Chex and the Rice Chex into one large bowl.
Melt chocolate, butter and peanut butter together in a microwave safe bowl for one minute. If the chocolate is not melted all the way, add 15 second intervals in the microwave so that you don't overcook it.
Stir in the vanilla into the chocolate mixture.
Pour the chocolate mixture over the Chex cereal. Mix to coat the cereal.
Put the chocolate coated cereal into a large ziploc bag. Add in the powdered sugar.
Seal the bag closed and shake to coat the cereal.
Spread the mix on a lined baking sheet.
Gently add the colored M&Ms and sprinkles. Chill in the fridge (or freezer) for 10 minutes to set the chocolate. Enjoy.