Preheat oven to 350. Mix crab meat, cheese, onions and mayonnaise. Spray 12 medium muffin cups with cooking spray. Gently place one won ton wrapper in each cup, allowing edges of wrappers to extend above sides of cups. Fill evenly with crab meat mixture. Bake 18 to 20 minutes or until edges are golden brown and filling is heated through. Serve warm. Garnish with chopped green onions, if desired.