Of course fluff is more of an art than a science, but here's one version for posterity:
2 (8 oz.) tubs of cool whip
2 small packets orange jello
1 (20 oz.) can pineapple tidbits, drained
mandarin oranges, drained (we used 2 cans totaling about 20 ounces)
1 bag of mini marshmallows
Mix it all together and refrigerate for a couple of hours before serving so the jello has time to dissolve.