Cook Acini Di pepe as package directs; drain. In a heavy saucepan, beat egg with wire whisk until foamy. Stir in sugar, flour, salt and reserved pineapple juice. Over low heat, cook and stir until thickened and bubbly. In a large bowl, combine acini di pepe with egg mixture. Chill thoroughly, about 1 hour. Stir in pineapple, fruit cocktail and marshmallows. Fold in whipped cream. Cover; chill thoroughly. Stir before serving.