01 -
Whisk the strawberry gelatin, cook-and-serve vanilla pudding mix, and water in a medium saucepan until smooth. Cook over medium heat, whisking often, until the mixture reaches a gentle boil and thickens slightly, 4-5 minutes.
02 -
Pour the hot mixture into a large heatproof mixing bowl. Cover and refrigerate until cold and thick, about 4 hours.
03 -
Use a hand mixer on medium speed to beat the chilled mixture until creamy, smooth, and loosened, about 1 minute.
04 -
Add the thawed whipped topping, sliced strawberries, drained pineapple, and mini marshmallows. Fold gently with a spatula until evenly combined.
05 -
Cover and refrigerate for at least 1 hour before serving. Garnish with extra strawberries and marshmallows if desired, then serve cold.