Crush 36 WHEAT THINS finely; place in medium bowl. Add peanut butter and sugar;beat with mixer until blended. Stir in cereal.
Spread 36 of the remaining WHEAT THINS with peanut butter mixture; cover with raining WHEAT THINS to make sandwiches, gently pressing WHEAT THINS into peanut butter mixture to secure.
Cover baking sheet with parchment. Dip half of each sandwich, 1 at a time, in melted chocolate; place on prepared baking sheet. Sprinkle with nonpareils. Refrigerate 30 min. or until chocolate is firm.