In a large mixing bowl, combine pineapple, pudding mix, marshmallows, and pecans.

Set aside 1/2 cup Cool Whip, refrigerating it until you're ready to serve the dish.

Fold the rest of the Cool Whip into the pudding-marshmallow mixture until the whole thing is tinted pastel green.

Refrigerate at least 45, or cover the bowl with plastic wrap and leave in the fridge overnight.

Place into individual serving cups and top with a spoonful of the remaining Cool Whip.

Sprinkle with chopped pecans and serve.