1 - 3 ounce package each of lemon and lime Jello. Drain 1 #2 1/2 can crushed pineapple and measure the liquid. Add enough boiling water to make just slightly less than 3 3/4 cup liquid. Melt the Jello in a flat bottom dish (10 x 6 3/4 inches) until Jello is dissolved. Add 1 pint (2 cups) vanilla ice cream and stir until completely melted. Add crushed pineapple and 1/2 cup chopped or ground pecans to the Jello and ice cream. Refrigerate as you would regular Jello and serve on lettuce leaves.