Prepare Gelatin: In a mixing bowl, dissolve the 1 (3 oz) package of orange gelatin in 1 cup of boiling water. Stir until completely dissolved. Once dissolved, add 1 cup of cold water to the gelatin mixture and stir well. Place the bowl in the refrigerator and let it cool until it begins to set but is not fully firm, which should take about 1 hour.
Combine Ingredients: In a large mixing bowl, combine the 1 (8 oz) container of whipped topping and the 1 (3.4 oz) package of instant vanilla pudding mix. Mix well until the mixture is smooth and creamy. Gently fold in the 1 (11 oz) can of drained mandarin oranges, the 1 cup of drained crushed pineapple, and the 2 cups of mini marshmallows (if using).
Mix in Gelatin: Carefully add the slightly set orange gelatin to the whipped topping mixture. Stir gently until all ingredients are well combined.
Chill: Cover the bowl and refrigerate the salad for at least 2 hours, or until it is fully set and chilled.
Serve: Before serving, give the salad a gentle stir to combine any ingredients that may have settled. Serve chilled and enjoy the refreshing taste!