Prepare the pudding: In a large mixing bowl, combine the instant pistachio pudding mix with the crushed pineapple (with juice drained) and stir well. The pudding mix will begin to thicken when combined with the pineapple juice, creating a creamy base.

1. Add the marshmallows and nuts: Fold in the mini marshmallows and chopped pecans (if using) into the pudding mixture. Stir gently to combine.
2. Fold in the whipped topping: Gently fold in the whipped topping, ensuring everything is mixed well and the mixture becomes light and fluffy.
3. Add coconut (optional): If you like, fold in the shredded coconut for an added tropical flair.
4. Chill: Cover the salad with plastic wrap and refrigerate it for at least 2 hours or overnight. The chilling time allows the flavors to meld together and the texture to set.
5. Serve and enjoy: After chilling, give the salad a quick stir, then serve it chilled in individual bowls or as a side dish at your next gathering.