Heat the olive oil in a cast-iron skillet over medium-high heat until hot, then add the pepperoni, onion, bell pepper and garlic. Cook until the onion has softened and the pepperoni has crisped slightly, about 3 minutes. Add the pizza sauce and crushed red pepper, then stir.
Add the rice and cook, stirring, until it is crisp and browned in spots, 2 to 3 minutes. Stir in the pineapple until it is warm and coated in the sauce, about another minute. Turn off the heat, then add the mozzarella, while continuing to stir, then tear half the basil and add it to the skillet. Taste and adjust the seasonings as needed. Serve immediately, garnished with the remaining basil torn over the top.