Prepare popcorn according to package directions. Remove all unpopped kernels. Place popped corn in large bowl sprayed with cooking spray.
Melt Fleischmann's in medium saucepan over medium heat. Add marshmallows and vanilla. Heat 5 minutes or until marshmallows melt, stirring frequently. Pour over popcorn; mix well with spoon sprayed with cooking spray. Moisten hands with water before shaping popcorn mixture into 24 small balls, about 1/3-cup popcorn mixture each.
Heat chocolate syrup in small saucepan over medium heat 5 minutes or until warm, stirring occasionally. Transfer to small fondue-style pot.
Use wooden skewers or fondue forks to pick up popcorn balls and dip into chocolate and sprinkles, if desired.