01 - Dissolve orange gelatin in 2 cups boiling water, stirring until fully dissolved. Add 1 cup cold water and mix well. Let cool for 10 minutes.
02 - Gently fold drained mandarin oranges and crushed pineapple into the cooled gelatin mixture.
03 - Transfer mixture to a 9x13-inch glass dish or decorative serving bowl. Refrigerate for at least 2 hours until completely set.
04 - In a separate bowl, fold together sour cream, mini marshmallows, and whipped topping until well combined and smooth.
05 - Once gelatin is fully set, spread the creamy mixture evenly over the top surface.
06 - Refrigerate for at least 1 additional hour before serving to allow layers to set together.
07 - Optionally garnish with extra mandarin orange segments or fresh orange zest just before serving.