Preheat your oven to 375°F (190°C). Lightly grease a 9-inch pie dish or oven-safe skillet.
In a medium bowl, mix the softened cream cheese, 1/2 cup sour cream, Italian seasoning, and garlic powder until smooth and well combined.
Spread the cream cheese mixture evenly in the bottom of the prepared dish.
Pour the marinara sauce over the cream cheese layer and spread gently to the edges.
Sprinkle 1 1/2 cups of mozzarella over the sauce, then scatter the mini pepperoni and black olives (if using) on top.
Bake for 18 to 20 minutes, until the cheese is melted, bubbly, and lightly golden at the edges.
While the dip cools for 2 to 3 minutes, put the remaining 1/4 cup sour cream in a small zip-top bag and snip a tiny corner.
Pipe the spider web: start with a small circle of sour cream in the center, then pipe 3 concentric circles around it. Drag a toothpick from the center outward through the circles (about 8 lines) to create the web effect.
Place the plastic spider on top for decoration if desired — just remember to remove it before serving! Serve warm with chips and bread.