01 - In a large mixing bowl, combine the instant pistachio pudding mix and undrained crushed pineapple. Stir well until the pudding mix is completely dissolved.
02 - Fold in the mini marshmallows and chopped nuts (if using).
03 - Gently fold in the thawed whipped topping until fully combined and the mixture is light and fluffy.
04 - Cover and refrigerate for at least 1 hour before serving to allow flavors to meld and marshmallows to soften.
05 - Just before serving, garnish with extra whipped topping, maraschino cherries, and additional chopped nuts as desired.