Place the peanut butter, sugar, and corn syrup into a 9 by 13 pan. Stir it and place in the oven for 5 minutes.
It should be mostly melted, remove from the oven and stir again, making sure to get the corners!
Place back in the oven for another 2 minutes.
Remove pan from the oven, stir well, and add the Rice Krispies.
Spray a large large spoon, or use a silicone spatula, and flatten out the top the the bars.