Grease a 9 by 13 inch pan and set aside.
Melt the margarine and marshmallows in a large bowl, I use the microwave and heat the mixture in one minute intervals, stirring after each minute until melted.
Add the cereal to the marshmallow mixture and stir well.
Press the mixture into the greased pan and let cool. Then cut into squares and place on a cookie sheet.
Melt chocolate chips or candy coating. Drizzle on top of the rice crispy squares. Sprinkle with sprinkles, if desired. Let cool until the chocolate or candy coating is set.