01 - In a large mixing bowl, combine instant pistachio pudding mix and undrained crushed pineapple. Stir thoroughly until pudding mix is completely dissolved.
02 - Fold in mini marshmallows and chopped nuts if using. Mix gently to distribute evenly.
03 - Gently fold in thawed whipped topping until fully combined and mixture is light and fluffy, taking care not to deflate.
04 - Cover bowl and refrigerate for at least 1 hour before serving to allow flavors to meld and marshmallows to soften properly.
05 - Just before serving, top with extra whipped topping, maraschino cherries, and additional chopped nuts as desired.