In a large mixing bowl, whisk together the instant pistachio pudding mix and the canned crushed pineapple. Beat this mixture for about 2-3 minutes until it thickens.

Gently fold in the thawed Cool Whip into the pistachio-pineapple mixture, ensuring a smooth blend while maintaining a fluffy texture.

Stir in the mini marshmallows and half of the chopped pecans or walnuts, gently combining them throughout the salad.

Transfer your mixed creation into a serving bowl and cover it tightly with plastic wrap. Refrigerate for at least 1 hour to allow flavors to meld.

Before serving, sprinkle the remaining chopped pecans or walnuts on top and garnish with maraschino cherries.