Cook orzo pasta to al dente, according to package instructions. Drain pasta, rinse and allow it to cool.
Drain the juices from the mandarin oranges, pineapple chunks, crushed pineapple and maraschino cherries into a large sauce pan (so you'll have mandarin orange juice, pineapple juice and maraschino cherry juice).
Reserve the fruit in a separate mixing bowl, cover and refrigerate. Over low to medium heat, whisk in the eggs, sugar, flour and cornstarch to the juices in the sauce pan.
Allow juice mixture to simmer for 5 to 7 minutes. It will thicken up during this time, stir occasionally.
Once thickened, remove from heat and set aside to cool for about 20 minutes.
Add orzo pasta to a large mixing bowl and pour thickened juices over top. Stir well to evenly coat pasta. Cover tightly and refrigerate overnight (or at least 8 hours).
When ready to serve, remove pasta from refrigerator, uncover, and use a large spoon to fluff the pasta. Stir in the reserved pineapple, mandarin oranges, and maraschino cherries along with the whipped topping.