In a large pot over medium-low heat, melt butter. Stir in marshmallows and peanut butter, and stir until mixture is melted. Remove from heat and stir in Rice Krispies. Let cool slightly. 

Step 2Line a baking sheet with parchment. Flatten about a tablespoon amount of Rice Krispies and add a mini Reese's in the middle and roll into a ball. Dip in melted chocolate, then place on prepared baking sheet. Sprinkle with sprinkles and repeat with remaining Rice Krispies. Refrigerate 20 minutes or until chocolate is set.