In a microwave or in a large saucepan over low heat, melt marshmallows, oil and extract if using; stir until smooth. Remove from heat; stir in cereal, banana chips, peanut butter chips and 1/2 cup peanuts. Press mixture into a lightly-greased 13x9-in. baking pan using wax paper or a lightly-greased spatula; press remaining 1/2 cup peanuts on top. Cool to room temperature. Cut into bars.