Pop the popcorn using an air popper or microwave method until fully popped, then transfer to a large mixing bowl. Ensure the popcorn is roughly uniform in size for even coating.
In a saucepan, melt the butter over medium heat, listening for a gentle bubbling sound. Once melted, add the corn syrup and sugar, stirring constantly with a spatula.
10 cups popped popcorn
Bring the mixture to a gentle boil while stirring constantly, continue cooking until it thickens slightly and turns a light amber color, about 3-4 minutes. Remove from heat and stir in vanilla extract.
10 cups popped popcorn
Pour the hot syrup evenly over the popcorn in the mixing bowl. Use a spatula to gently fold and coat all the popcorn thoroughly, watching for a shiny, sticky surface to develop.
Add the colorful candies and cheese crackers to the coated popcorn. Gently toss to distribute all toppings evenly, ensuring they stick to the sticky surface.
10 cups popped popcorn
Transfer the mixture either onto a baking sheet to cool and set or serve directly in a large bowl. Allow to sit for about 10 minutes until the coating firms up and the mix becomes crisp and colorful.