In a medium bowl, blend the cream cheese, ½ cup mozzarella cheese, 1 thinly sliced green onion, and 1 teaspoon garlic powder. Press into the bottom of a pie plate.
Layer tomatoes and bell peppers over the cream cheese mixture.
Spoon pizza sauce over the tomatoes and peppers.
Layer mushrooms, remaining green onion slices, and pepperoni pieces over the pizza sauce.
Spread cheddar cheese over the pepperoni pieces.
Sprinkle remaining mozzarella cheese over the cheddar cheese.
Top with whole pepperoni slices if desired and sprinkle with a few green onion slices, bell pepper pieces, and/or parsley.