Put the Orange Jell-O and boiling water in a big bowl.
Stir until the Jell-O has fully dissolved.
Add the cold water and refrigerate for 15 minutes.
Gradually mix in the Vanilla Pudding mix until it's smooth and return it to the refrigerator for another 15 to 20 minutes, or until it starts to thicken.
Gently fold in the Cool Whip, Mandarin Oranges, and Mini Marshmallows.