Place the Chex, Cheerios and pretzels into a gallon sized freezer bag..
Place the chocolate in a microwave safe bowl and heat it in the microwave at 15 second intervals. Stir in between intervals until the chocolate becomes smooth.
Pour the chocolate over the cereal mixture in the bag.
Close the bag and shake it until the cereal is covered in chocolate.
Add M&Ms and Christmas sprinkles.
Spread the mixture out on the baking sheet.
Place in the fridge until the chocolate hardens (about an hour).