Bring a large pot of water to a boil. Add the acini di pepe pasta and cook according to package directions until tender.
1 cup acini di pepe pasta
Drain the pasta and rinse under cold water until completely cooled. Set aside.
In a medium saucepan, whisk together the eggs, sugar and flour until smooth.
2 eggs, 3/4 cup sugar, 2 tbsp flour
Stir in the reserved pineapple juice and enough water to equal 1½ cups total liquid.
1 1/2 cups liquid
Cook over medium heat, whisking constantly, until the mixture thickens into a pudding-like consistency, about 5–7 minutes.
Let the mixture cool completely before using.
In a large bowl, combine the cooled pasta, pineapple tidbits, mandarin oranges, mini marshmallows, and coconut.
1 20 oz can pineapple tidbits, 1 15 oz can mandarin oranges, 2 cups mini white marshmallows, 1/2 cup sweetened shredded coconut
Pour the cooled pudding mixture over everything and stir gently until combined.
Fold in the whipped topping until evenly incorporated.
1 8 oz tub whipped topping
Cover and refrigerate for at least 4 hours, preferably overnight, before serving.
Stir gently before serving and serve chilled.