Mix pudding and pineapple. In a large bowl, combine the undrained pineapples and the pistachio instant pudding mix. Stir together until the pudding mix is fully dissolved. Place the bowl in the refrigerator for 5 minute to let the pudding firm up.
CAN WATERGATE SALAD BE MADE A DAY AHEAD? Yes! In fact I recommend you make it the night before, or first thing in the morning on party day. When it can sit in the refrigerator, all of those flavors will meld together, the marshmallows will soften a little, and the Watergate Salad will firm up a little.