Preheat the oven to 400ºF and grease a 2-quart baking dish with cooking spray; set aside.
In a medium bowl, add cream cheese, 1 cup sharp Cheddar cheese, Parmesan cheese and Italian seasoning.
Combine the ingredients before spooning the cheese mixture into the prepared baking dish; spread it out evenly. Add pizza sauce and spread it out as well.
Evenly distribute half mini pepperoni and half sliced black olives; set aside.
In a skillet over medium heat, add Italian sausage and cook halfway, breaking the meat into small pieces.
Add yellow onions and green peppers; sauté for 2 minutes. Add mushrooms, stir to coat and cook for 3 to 4 minutes.
Add pressed garlic and sauté for only 1 minute.
Using a slotted spoon, add meat mixture to baking dish. Add remaining mini pepperoni, remaining sliced black olives and top with remaining 1 cup Cheddar cheese.
Transfer the baking dish to the preheated oven and bake for 22 to 25 minutes or until the cheese is melted and bubbly.
Remove from the heat and let it rest a couple minutes before serving.