Step 1: Grease a 9x9 inch baking pan or line it with parchment paper.
Step 2: In a large pot, melt the butter over low heat until smooth.
Step 3: Add the mini marshmallows and stir continuously until completely melted and well combined with the butter.
Step 4: Remove from heat and stir in the vanilla extract.
Step 5: Fold in the rice cereal until evenly coated with the marshmallow mixture.
Step 6: Quickly fold in the crushed animal cookies and half of the sprinkles.
Step 7: Gently press the mixture into the prepared pan without compacting it too firmly.
Step 8: Top with whole cookies, remaining sprinkles, and a drizzle of melted white chocolate.
Step 9: Let cool at room temperature for 1 hour before cutting into squares.