In a mixing bowl, combine ground beef, ground pork, breadcrumbs, Parmesan cheese, parsley, garlic, egg, salt, pepper, and Italian seasoning. Mix until combined.
Shape the mixture into meatballs, about 1 inch in diameter.
If desired, broil the meatballs on a baking sheet for 5 minutes to create a nice crust.
Place the meatballs in the crockpot.
Pour the marinara sauce over the meatballs. Make sure they are well coated.
Cover and cook on low for 6 hours or on high for 3 hours.
Once cooked, carefully remove the meatballs with a spoon and serve hot, garnished with extra parsley if desired.