In large microwavable bowl, mix cereal, peanuts and pretzels.
In 2-cup microwavable measuring cup, microwave butter, brown sugar and corn syrup uncovered on High 2 minutes, stirring after 1 minute; stir until smooth. Stir in baking soda until foamy. Pour over cereal mixture, stirring until evenly coated.
Microwave uncovered on High 1 to 2 minutes, stirring and scraping bowl every 30 seconds, just until cereal begins to brown. Cool 5 minutes; stir in candies. Spread on waxed paper or foil to cool; break into bite-size pieces. Store in airtight container.