Cook ground beef in a skillet over medium heat until no longer pink, breaking it apart into crumbles as it cooks, about 10 minutes.
Bring a large pot of lightly salted water to a rolling boil. Cook egg noodles in boiling water until cooked through yet slightly firm, about 5 minutes; drain.
Mix noodles with cooked ground beef, spaghetti sauce, black olives, mushrooms, pepperoni, and half of the mozzarella cheese in a large mixing bowl. Spoon mixture into a 9×13-inch baking dish and top with remaining cheese. Cover dish with foil.
Bake in preheated oven until casserole is bubbling, 30 to 45 minutes.
