Preheat oven to 375.
In a microwave safe bowl microwave cream cheese for 30 seconds to warm it. Add sour cream, shredded mozzarella cheese, onion powder and 3/4 of the chopped pepperoni.
Spray a baking dish with cooking spray (or use an aluminum pan if going to a party and you don't want to worry about dishes.) Spread dip into the baking dish. Place remaining pepperoni on top. Bake for 20-25 minutes, until the edges are starting to turn golden brown.
Serve with crackers and enjoy!