Preheat oven to 350°F (175°C).
In a large bowl, combine the cooked shredded chicken, cream of chicken soup, sour cream, shredded cheddar cheese, cooked rice, and chopped green onions. Mix until evenly combined.
Transfer the mixture to a greased square or rectangular casserole dish and spread evenly.
In a small bowl, mix the melted butter with the crushed Ritz crackers until well coated.
Sprinkle the buttered cracker mixture evenly over the casserole.
Bake in the preheated oven for 30-35 minutes or until the topping is golden brown and the casserole is bubbly.
Remove from oven and let sit for 5 minutes before scooping onto a round white plate to serve.