In a large microwave safe container, heat butter and mini marshmallows for 1 minute in the microwave.
Stir marshmallow mixture until fully melted. Heat for 15-30 second increments if more melting is needing.
Stir rice krispies cereal, 1 tablespoon of nonpareils, and 2 cups chopped animal cookies into melted marshmallows.
Spread into greased baking dish. Allow to cool completely (at least 30 minutes).
In separate bowls, heat candy melts in the microwave at 30 second increments, stirring between each heating, until just melted.
Transfer candy melts into piping bags or plastic Ziploc baggies. Snip a small hole in the point (or in the corner of the baggy) and drizzle over the cooled rice krispie treats.
Immediately top with whole cookies and more nonpareils. Allow candy melts to set and harden (about 15 minutes). Cut and serve.