Line one 9×13 inch baking pan with the graham cracker or vanilla wafer crumbs. Reserve a few crumbs as a garnish for the top.
Drain the pineapple, saving the juice. Melt the marshmallows in the pineapple juice over low heat. Once melted set aside to cool.
Cut up the bananas into chunks. Mix the bananas, chopped nuts, and crushed pineapple into the cooled marshmallow mixture.
Fold the fruit mixture into the whipped cream. Spoon batter into the graham cracker or vanilla wafer lined pan. Sprinkle the reserved crumbs on top. Chill well before serving. Makes about 12 to 18 servings.