With a hand or stand mixer, combine the softened cream cheese with one cup of the shredded mozzarella, Parmesan and Italian seasoning. You can also stir it by hand. Spread the cream cheese mixture evenly into the bottom of the slow cooker insert.
In a large non-stick skillet over medium heat, brown the sausage and add the pizza sauce. Stir until well combined. Pour it over the cream cheese layer in the slow cooker insert.
In the same skillet that you've wiped clean, cook the pepperoni until starting to crisp. You can drain the pepperoni before adding it to the slow cooker. It's up to you.
Top the sauce layer in the slow cooker with the remaining one cup of shredded mozzarella cheese. Top the cheese with the crisp pepperoni.
Cook on high heat for one hour before serving. Turn to the warm setting to serve.