Heat the rice cereal on a 15 1/2 X 10 1/2 X 1-inch jelly roll pan in a 350 degree F. oven for 10 minutes. Meanwhile, combine the butter, marshmallow creme and peanut butter in the top of a double boiler. Place over hot water and stir until melted. Remove from the heat. Place the cereal in a large buttered bowl. Pour the peanut butter mixture over all and mix well. Turn the mixture into an aluminum foil lined 9-inch square baking pan. Press into an even layer. Cool and cut into 36 (1 1/2-inch) squares.