In a medium saucepan, whisk together pudding mix, Jello mix, and water. Cook over medium heat and bring to a boil.
Remove saucepan from heat and pour into a large mixing bowl. Cover with plastic wrap.
Refrigerate until mixture has thickened (overnight or for about 4-6 hours).
Once mixture has thickened, beat until creamy with an electric hand mixer.
Fold in Cool Whip, marshmallows, and fruit. Chill for about an hour before serving.
Notes
Using bananas is optional in this recipe (it's great with or without them), but if you do use them, add them right before eating. They tend to turn brown and get mushy if you add them too early.