Line a large sheet pan with parchment paper and set aside.
Add the candy melts (if using one color, separate it into 3 parts and if using different colors, place about 1/3 of each color) into microwave safe bowl(s).
Add about 1 teaspoon shortening or vegetable oil if desired (optional, it just makes for smoother/easier application of the chocolate to the krispie treats) to each bowl of chocolate. (I use 1 teaspoon shortening to each 1/3 of chocolate candy melts)
Microwave (one bowl at a time) of candy melts in bursts of 20 seconds, stirring vigorously in between each burst for 10 seconds.
Meanwhile, upwrap the krispies treats.
Once the chocolate is smooth, dip the krispie treats in the melted chocolate and then use a spoon to help spread it over the treat. You want it to be a bit ragged to look more like a monster.
Working quickly (the melted candy melts harden fast), add candy eyeballs (however you want and whatever size you like) and if desired, colored sprinkles.
Transfer to the prepared sheet pan and allow for the chocolate to set at room temperature. These are best enjoyed the same day they are made.