Preheat your oven to 375°F (190°C). Use a sharp knife to carve spooky eyes and mouths into each bell pepper, creating a Halloween face. Carefully remove the tops and seeds to form a hollow shell.
In a mixing bowl, combine the cooked rice, diced tomatoes, chopped onion, minced garlic, shredded cheese, and a splash of olive oil. Season with salt and pepper, then stir until well mixed.
Spoon the filling mixture into each carved pepper, pressing lightly to pack it in and ensure it's rounded on top. Fill each pepper until they are slightly overstuffed.
Place the stuffed peppers upright in a baking dish, ensuring they sit securely without tipping over. Cover the dish loosely with foil to help retain moisture.
Bake the peppers in the preheated oven for about 30 minutes, until the peppers are tender and the filling is bubbling and slightly browned on top.
Remove the dish from the oven and let the peppers cool for a few minutes. Carefully transfer them to a plate, and serve hot to enjoy the gooey, flavorful filling and festive carved faces.