In a large pot, melt butter over medium-low heat until completely liquefied, then add marshmallows. Stir continuously until melted and smooth, then remove from heat.

Gently fold in crispy rice cereal using a greased rubber spatula until evenly coated.

Transfer the mixture into a parchment-lined 9x9 inch pan, pressing it down firmly. Let it cool for about 40 minutes to set completely.

In a microwave-safe bowl, melt candy melts in 45-second intervals, stirring until smooth.

Carefully dip each cooled Rice Krispie treat into the melted candy, using a butter knife to smooth any excess. Set them on parchment paper to dry.

While the candy coating is still warm, gently press on the candy eyeballs and sprinkle colorful sprinkles. Allow to set for 45 minutes.