Preheat and prep pan: Preheat your oven to 400°F and line a sheet pan with parchment paper or set a wire rack over it. This keeps the meatballs from sitting in their own juices so the outsides brown evenly.

Mix the meatball base: In a large bowl, combine ground beef, egg, breadcrumbs, Parmesan, garlic, Italian seasoning, salt, and pepper. Mix with clean hands just until blended, about 1 minute; overmixing makes the meatballs tough.

Portion the meat: Divide the mixture into 16 equal portions, roughly 2 tablespoons each. Flatten each portion into a small disk in your palm.

Stuff with mozzarella: Press one mozzarella ball into the center of each meat disk. Fold the edges of the meat up and around the cheese, then roll gently between your palms until the seam closes and the ball looks smooth.

Arrange and bake: Place the stuffed meatballs on the prepared pan, spacing them about 1 inch apart. Bake for 18 to 20 minutes, until the outside is browned and firm to the touch.

Boil the spaghetti: While the meatballs bake, cook spaghetti in a large pot of salted boiling water according to the package directions, about 9 minutes, until just tender. Drain, reserving 1/4 cup of pasta water.

Warm the sauce: In a separate saucepan, heat the marinara sauce over medium-low until it just starts to bubble around the edges, about 5 minutes. Toss the drained spaghetti with most of the warm sauce, adding a splash of reserved pasta water if it looks dry.

Add the olive pupils: As soon as the meatballs come out of the oven, press one olive slice into the top of each one so it sinks in slightly and sits like a pupil in the mozzarella eye.

Plate and serve: Divide the sauced spaghetti among plates or a large serving platter. Nestle the meatball eyeballs on top, spoon over the remaining marinara, and scatter fresh basil over everything before bringing it to the table.