Stir in 1/2 cup marshmallows.
Heat griddle over medium-high heat. Spray with cooking spray.
For each pancake, pour slightly less than 1/4 cup batter onto hot griddle. Cook about 3 minutes or until bubbles form on top and edges are dry. Turn; cook other side until golden brown and set.
Top pancakes with whipped cream topping and additional marshmallows, if desired.