Bring a large pot of lightly salted water to a boil. Cook Halloween-shaped and wagon wheel-shaped pasta in the boiling water, stirring occasionally until cooked through but firm to the bite, about 12 minutes. Drain and transfer pasta to a large bowl.
Place pumpkin in a large pot and cover with salted water; bring to a boil. Reduce heat to medium-low and simmer until tender, about 20 minutes. Drain and return pumpkin to pot. Add nutmeg, allspice, cinnamon, 1 teaspoon garlic, onion, chili powder, and 3 tablespoons olive oil; stir to coat.
Toss olives and garbanzo beans into cooked pasta. Add 1/4 cup garlic, Parmesan cheese, 1/4 cup olive oil, and oregano. Toss to coat; top with pumpkin mixture.