In a saucepan over medium heat, combine the sugar and corn syrup, and bring to a rolling boil. Remove from heat, and stir in peanut butter. Mix in the rice cereal until evenly coated. Press the mixture into buttered 13x9x2-inch pan.
Melt the chocolate and butterscotch chips, stirring occasionally until smooth and well blended. Spread over the top of the bars. Chill until set, then cut into bars.