Place the whipped topping, pudding mix and yogurt into a large bowl. Whisk together. Cover and refrigerate until just before serving (at least an hour).
When you are ready to serve, slice the strawberries and bananas.
Remove whipped cream/pudding mixture from refrigerator and gently fold in sliced strawberries, berries, sliced bananas and marshmallows, and stir gently to combine.
Serve immediately.