Preheat the oven to 375°F (190°C). Lightly grease a baking dish.
In a large bowl, mix cream cheese, mayonnaise, and sour cream until smooth.
Stir in ¾ cup cheddar cheese, Parmesan cheese, Old Bay seasoning, garlic powder, and hot sauce.
Gently fold in crab meat and green onions.
Transfer the mixture to the baking dish and top with the remaining cheddar cheese.
Bake for 20-25 minutes, until bubbly and golden.
Garnish with extra green onions and Old Bay seasoning. Serve warm.