Preheat the oven to 325°F. Prepare large baking sheets by lining them with parchment paper or silicone baking mats. If you don't have these things, cover baking sheets with aluminum foil and spray them with cooking spray to make sure nothing sticks.
Add the pretzels, salted peanuts, Chex, and Bugles to a large bowl (or two large bowls) and mix together. Make sure this is ready to go because once the butter sauce is ready, you need to move fast!
Add 2 sticks of unsalted butter and 1 cup of brown sugar to a small saucepan. Bring the mixture to a boil over medium heat and let boil for 3 minutes. Make sure to stir regularly so the mixture doesn't burn and become bitter.
The mixture will become quite thick and dark brown. Remove the mixture from the heat and stir in 1 tablespoon of vanilla extract, 2 teaspoons of cinnamon, and 1 teaspoon of kosher salt.
Immediately pour over the salty snacks and Chex mixture, and mix quickly to coat as quickly as possible. If you'd like, you can stop here, but we do highly recommend baking the mixture for the best flavor and more crunch!
Place the mixture on the lined baking sheets. Put in the oven and bake for 10 minutes, take the mixture out and carefully mix everything around. Put back into the oven for another 10 minutes, take the mixture out again and toss, then return to the oven for another (final) 10 minutes.
After the full 30 minutes is up, allow to cool completely. After the snack mix is completely cooled, you can transfer it to a serving bowl or platter, and add the candy, chocolate pieces, sprinkles, and googly eyes. Toss to combine, and serve!
Serve immediately or put in an airtight container like a ziplock bag and store in a cool, dry place at room temperature for up to 7-10 days. Refrigeration is not necessary, but, you can store them in the fridge if it's warm in your kitchen. Do not freeze.