Preheat oven to 300 degrees and lightly spray a large baking sheet.
In a large bowl, add the popcorn, cereal, and pretzels. It's best if you use a bowl with a lid so you can just shake it up for mixing. Mix everything together and set aside.
In a small saucepan, add the brown sugar, butter, and corn syrup. Stir over medium heat until the mixture comes up to a boil.
Once boiling, let the pan boil without stirring for 5 minutes.
Remove from heat. Add the vanilla and baking soda. Mix it all together.
Quickly pour the caramel mixture into the large popcorn bowl, close the lid and mix everything together. If you don’t have a lid just use a spatula and toss it together. Move quickly as the sauce will harden.
Pour the snack mix onto your prepared baking sheet and place in the preheated oven. Bake for 15 minutes, toss everything around and then bake for another 15 minutes.
Once done, spread it out over wax paper or parchment paper on the countertop until it’s cooled.
Add in the chocolate candies after the mixture is cooled so they don’t melt everywhere. Toss everything together and serve! Store in an airtight container.
8 cups of popped popcorn equals about 3/4 of a full-size bag of microwave popcorn