Make sure to remove any unpopped popcorn kernels from the bowl. Then mix together popcorn and peanuts.
In a large saucepan or dutch oven, bring sugar and corn syrup just to a boil.
When all of the sugar is dissolved and the mixtures is bubbly, remove from heat. Stir in peanut butter and vanilla.
Add popcorn and peanuts, stirring to coat everything evenly with the peanut butter mixture.
Allow to cool until safe to handle. Grease your hands and grab a handful of the popcorn mixture. Form into a ball, pressing slightly to help it hold together.
Place on a sheet of wax paper to cool completely, then wrap in plastic wrap until ready to serve.