Preheat oven to 375 degrees and lightly grease an 8-inch square baking dish.
Combine cream cheese, sour cream, mayonnaise, milk, garlic and onion powder, cajun seasoning, and red pepper flakes in a large bowl and mix with a hand held electric mixer until smooth.
Stir in broccoli, mozzarella cheese, and cheddar cheese.
Transfer mixture to prepared dish. Sprinkle cracker crumbs on top.