Preheat the oven to 350°F (175°C).

In a medium bowl, combine crushed pretzels, melted butter, and granulated sugar. Mix well.

Press the pretzel mixture into the bottom of a 9x13 inch baking dish to form a crust.

Bake the pretzel crust in the preheated oven for 10 minutes, then remove and let cool completely.

In a large mixing bowl, beat together softened cream cheese and powdered sugar until smooth.

Fold in the whipped topping, crushed pineapple, mini marshmallows, and chopped nuts (if using) until well combined.

Spread the pineapple mixture over the cooled pretzel crust evenly.

Chill in the refrigerator for at least 2 hours to set.

Before serving, garnish with red and blue sprinkles for a festive touch.