01 - In a large bowl, dissolve the orange gelatin in 2 cups boiling water. Stir until fully dissolved, then add 1 cup cold water. Mix well and let cool for 10 minutes.
02 - Gently stir in the mandarin oranges and crushed pineapple.
03 - Pour the mixture into a 9x13-inch glass dish or a decorative serving bowl. Refrigerate for at least 2 hours, or until set.
04 - In a separate bowl, fold together the sour cream, mini marshmallows, and whipped topping until well combined.
05 - Once the gelatin is fully set, evenly spread the creamy mixture over the top. Chill for at least 1 more hour before serving.
06 - Optionally, garnish with extra mandarin orange segments or a sprinkle of orange zest.