Line a large sheet pan with parchment paper and set aside.
Add candy melts to microwave-safe bowls. If using one color, divide it into three equal parts. If using multiple colors, place about 1/3 of each color into separate bowls. Optionally add shortening or oil for easier application of the chocolate to the krispie treats, 1 teaspoon to each 1/3 chocolate candy melts.
Microwave each bowl in 20-second bursts, stirring vigorously for 10 seconds between each burst until smooth.
Upwrap Rice Krispies Treats.
Once chocolate is smooth, dip Krispie Treats in melted chocolate and use a spoon to help spread it over the treat, giving it a ragged “monster” look.
Working quickly (the melted candy melts harden fast), press on candy eyeballs and sprinkles (if desired). Decorate however you’d like!
Transfer to the prepared sheet pan and allow chocolate to set at room temperature. Best enjoyed the same day they’re made.