In a large mixing bowl, combine the undrained crushed pineapple and the instant vanilla pudding mix. Stir until the pudding dissolves and the mixture begins to thicken.
Gently fold in the whipped topping until smooth and fully combined.
Add the mini marshmallows, shredded coconut, mandarin oranges, maraschino cherries, and chopped nuts, if using.
Fold everything together gently to avoid breaking up the fruit.
Cover the bowl and refrigerate for at least 2 hours to allow the flavors to blend and the marshmallows to soften.
Stir gently before serving.
Garnish with additional coconut, cherries, or chopped nuts if desired.