Preheat oven to 300°F. Spray 13x9-inch baking pan and twelve 2-1/2-inch muffin cups with cooking spray.
Prepare popcorn according to package directions. Remove any unpopped kernels. Spread popped corn evenly in baking pan.
Melt Fleischmann’s in medium saucepan over medium-high heat. Add sugar, corn syrup and salt; bring to a boil. Boil 2 minutes stirring constantly; remove from heat. Stir in baking soda; mix well. Pour over popcorn and toss gently to coat evenly.
Bake 5 minutes, stirring once halfway through baking. Remove from oven; stir well. Cool 5 minutes. Moisten hands with water. Divide popcorn mixture into 12 portions; shape each portion in each muffin cup to resemble a cupcake.
Spread frosting on the top mounded part of each popcorn cupcake. Add sprinkles and candle, if desired. Store in tightly sealed container.