Make Rice Krispie Treats (there is almost always a recipe for them on the back of marshmallow bags or Rice Krispie Cereal boxes).
Cut rice krispie treats into rectangles.
Make sure you have monster eyes. I made my own eyes using Royal Icing. You just need some white and some black (or brown, I opted for using chocolate). On wax paper, make a larger circle with white and then a smaller black circle on it. Let the icing dry and harden before peeling them off the wax paper. I let mine sit overnight. I made my own because I used eyes on a ton of party food items, but if you don’t want to make your own they can also be purchased at Walmart or any crafting or baking goods store. I also found them on Amazon: Wilton Candy Eyeballs.
Use royal icing dyed the colors of your choosing. Drizzle the icing on the rice krispie treats. Be sure to make the bottom portion look like it is dripping. Add monster eyes to the icing, let the icing harden and you are done! If you don’t want to use icing, you could also use colored candy melts. Candy melts even come in fun flavors so you could have flavored Monster Rice Krispie Treats too.