Spray a 9-inch cake pan with non-stick cooking spray and set aside.

Combine 4 ounces of marshmallows (16 regular marshmallows or 2 ½ cups minis) and 1 ½ tablespoons of butter in a large saucepan over medium-low heat. Stir continuously until the marshmallows and butter have melted and the mixture is smooth.

Remove from the heat and stir in ¼ teaspoon of vanilla, a pinch of salt, and 4-5 drops of green food color.

Add 1 ¾ cups of rice krispies cereal and stir until evenly coated in the green marshmallow mixture.

Turn the mixture out into the prepared cake pan. Lightly spray your fingertips with cooking spray and shape the treats into a ¾-1 inch ring around the outside of the pan. Set the pan aside while you make the center of the watermelon.

Add the remaining 6 ounces (24 regular marshmallows or 3 ½ cups minis) and 2 ½ tablespoons of butter to a clean medium saucepan over medium heat. Stir continuously until the mixture is melted and smooth.

Remove from the heat and stir in the remaining ¾ teaspoon of vanilla, a pinch of salt, and 4-5 drops of pink or red food color.

Add the remaining 2 ¾ cups of rice krispies and stir until evenly coated with the pink/red marshmallow mixture.

Turn the pink/red treats into the center of the prepared cake pan and press down to create the center of the watermelon.

Allow the rice krispies treats to cool for about 5 minutes, then press the mini chocolate chips 1 at a time into the red treats to create the watermelon seeds.

Allow the treats to set at room temperature for at least 1 hour before cutting into 6-8 wedges and serving.