In a large skillet, over medium-high heat, cook the sausage and green bell pepper breaking up the sausage as it cooks. When it's fully cooked, drain off the fat.
Put the cooked sausage and peppers in a large slow cooker. Add in the pepperoni, cream cheese, drained diced tomatoes, mozzarella, parmesan cheese, garlic powder, and Italian seasoning.
Cover and cook for 1-2 hours on high. Every so often, stir the dip to incorporate all of the ingredients. Garnish with fresh chopped parsley if desired.