In a large bowl, combine popcorn, cereal and peanuts, if desired; set aside.
Combine chocolate and peanut butter in a microwave-safe bowl. Microwave on high 2 to 3 minutes or until melted, stirring after every minute.
Pour over popcorn mixture, tossing to coat well. Spread onto a large greased non-stick baking sheet; cool completely. Break apart; store in an airtight container up to 5 days.