Prepare your workspace and tools: have a large mixing bowl and a sturdy spoon or spatula ready. Make sure the whipped topping is fully thawed and chilled for easiest folding.
Open the can of crushed pineapple and pour it into the large bowl, including all the juice.
Sprinkle the banana cream instant pudding mix over the pineapple and its juice. Stir continuously until the pudding mix is fully dissolved and the mixture looks uniform—this usually takes about 1 to 2 minutes.
Gently fold the whipped topping into the pineapple-pudding mixture using a spatula. Fold slowly until everything is evenly combined and light and airy; avoid overmixing to keep the fluff texture.
Transfer the finished fluff to a serving bowl or individual cups. Cover and refrigerate for at least 1 hour before serving to allow the flavors to meld and the texture to set.
Serve chilled. Optional: garnish with maraschino cherries, sliced bananas, chopped pecans, mini chocolate chips, or a sprinkle of crushed cookies right before serving for extra flair and texture.
Notes
Store leftovers in an airtight container in the refrigerator for up to 3–4 days. Stir briefly to refresh texture if it has separated slightly.