Chill your tools: For the fluffiest texture, place a large mixing bowl and spatula in the fridge for 10 minutes before you start.
Mix the creamy base: In the cold bowl, stir together the whipped topping and sour cream until smooth.
Add the vanilla and a pinch of salt. The salt helps balance the sweetness.
Fold in the fruit: Add the cherry pie filling and the well-drained crushed pineapple. Gently fold to keep the mixture airy.
Avoid overmixing; visible streaks are okay at this stage.
Add the mix-ins: Fold in the mini marshmallows. If you’re using nuts and coconut, add those now. The nuts bring crunch, and the coconut adds chew and a little extra sweetness.
Check the consistency: The mixture should be thick but scoopable.
If it feels too loose, add another small handful of mini marshmallows.
Chill to set: Cover the bowl and refrigerate for at least 2 hours, or up to overnight. Chilling lets the marshmallows soften and the flavors blend.
Stir and serve: Before serving, give it a gentle stir. Spoon into bowls or a serving dish.
For a pretty finish, top with a few extra cherries, a sprinkle of coconut, or chopped nuts.