In a large mixing bowl, beat the softened cream cheese and the dry pistachio pudding mix together until the mixture is light and wonderfully fluffy.
Carefully stir in the crushed pineapple, making sure to include all of its natural juice for extra moisture and a burst of flavor.
Gently fold in the miniature marshmallows until they are well combined throughout the creamy filling.
Now, lightly fold in your Cool Whip or freshly whipped heavy cream until the mixture is just blended and beautifully airy.
Spoon this delightful green filling into your prepared pie crust, spreading it out evenly.
Place the pie in the refrigerator and chill for at least two hours, or until it's perfectly set and firm.
For an optional beautiful garnish: If desired, whip the extra 1 cup of heavy cream with the powdered sugar until it forms stiff peaks. Pipe this creamy topping onto your chilled pie.
Finish with a sprinkle of chopped pistachios and a few vibrant maraschino cherries for a festive touch. Serve and enjoy your easy, no-bake treat!