In a medium bowl, combine the cream cheese, spinach, mozzarella, salt, pepper, and garlic powder, stirring until thoroughly mixed. Transfer the mixture to a square baking pan lined with parchment paper and spread the mixture evenly in the dish. Freeze for 30 minutes.
Invert the frozen spinach dip onto a cutting board and remove the parchment paper. Slice the block into 1-centimeter strips, then slice the strips in half into sticks.
Place the flour, eggs, and breadcrumbs into three separate bowls. Dip the spinach dip sticks into the flour, then the eggs, then the breadcrumbs, then back into the eggs, and finally back into the breadcrumbs. Set the breaded sticks aside on a plate.
Heat oil in a pot over medium-high heat. Fry the breaded sticks for about 30 seconds to a minute, until golden brown.
Cool, then serve with marinara sauce!