Grease a 12" pizza pan with nonstick cooking spray and press cookie dough into pan. Bake for 12-15 minutes or until golden brown. Add marshmallows to the top of the cookie and bake for an additional 2-3 minutes until marshmallows are puffy. Remove from oven and cool completely. 

Set aside about 1/4 cup white icing, or one large spoon dollop. Divide remaining frosting in half and place into two separate dishes. Color one dish teal and one dish purple. Set aside about 3 tablespoons of each of the colored frosting (place them in a small microwave safe bowl, this is the drizzle frosting). 

Microwave two small bowls of icing for 10 seconds. Stir. If the mixture isn't easily pour-able, return to microwave for 5 seconds. Mix well and drizzle with a spoon over the pizza. Top with mermaid sprinkles and Sixlets. 

Lay a piece of plastic wrap onto a flat surface. Spread each of the 3 colors of icing next to each other on the plastic wrap, making about a 10-12" strip. Fold the plastic wrap tightly and twist ends. 

Snip the tip of the plastic wrap and place into a plastic piping bag fitted with a star tip. Pipe icing onto the outer edge of the pizza. 

Top with mermaid decorations and slice and eat. 

To store, loosely cover and store at room temperature.