In a large mixing bowl, combine the mini marshmallows, shredded coconut, mandarin oranges, and pineapple chunks. Gently fold the ingredients together until evenly mixed.
In a separate bowl, mix the sour cream, chopped nuts, and vanilla extract until well combined.
Pour the sour cream mixture over the fruit and marshmallow mixture. Gently fold everything together until all ingredients are coated.
Cover the bowl with plastic wrap and refrigerate for at least 2 hours to allow the flavors to meld.
Serve chilled, garnished with additional coconut or nuts if desired.