In a big bowl, mix the Orange Jell-O and Instant Vanilla Pudding powders together.
Add 1 cup of hot water and stir until both the Jell-O and pudding powders are fully dissolved.
Put half a cup of cold water in the bowl and mix until well combined.
Let the gelatin mixture cool for around 2 minutes.
Carefully mix in the Cool Whip until smooth and creamy.
Add the mandarin oranges and marshmallows.
