Break blocks of noodles in half (reserve one seasoning packet; discard second packet); set aside. In 10-inch skillet, cook beef and pepperoni over medium heat 8 to 10 minutes, stirring occasionally, until beef is brown; drain.
Stir tomatoes, water and reserved seasoning packet into beef mixture. Heat to boiling. Stir in noodles and bell pepper. Cook 3 to 5 minutes, stirring occasionally, until noodles are tender.
Sprinkle cheese on noodle mixture in ring around edge of skillet. Cover and let stand about 5 minutes or until cheese is melted.