In a large mixing bowl, combine the instant pistachio pudding mix and the undrained crushed pineapple, including its juice. Blend together thoroughly for about 2 minutes until well combined and thickened.

Gently fold in the thawed whipped topping using a rubber spatula for about 1-2 minutes until smooth and uniformly green.

Add the mini marshmallows and half of the chopped pistachios, stirring gently to combine for about 1 minute.

Cover the bowl with plastic wrap and refrigerate for at least 1 hour to allow flavors to meld.

Before serving, remove from the refrigerator and sprinkle with the remaining chopped pistachios, maraschino cherries or shredded coconut as desired.