Line a baking sheet with parchment paper. Open the candy eyeballs and sprinkles, then place them within easy reach so they are ready to add before the candy coating begins to set.

Working with one color at a time, place ¼ cup of candy melts in a small microwave-safe bowl. Microwave in 30-second intervals, stirring well after each interval, until the coating is completely melted and smooth.

Hold one Nutter Butter by the bottom and dip the top half into the melted candy coating. Lift the cookie from the bowl and gently tap off the excess, allowing it to drip back into the bowl.

Place the dipped cookie on the prepared baking sheet. Immediately add one or more candy eyeballs and matching sprinkles while the coating is still wet.

Repeat with the remaining cookies, melting the blue, green, and orange candy separately. Leave the finished cookies at room temperature for 10 to 15 minutes, or until the candy coating is completely firm.