The "NCIS" franchise, inspired by the real Naval Criminal Investigative Services, has expanded over the years to include multiple shows. The original "NCIS" series has been on the air the longest, with 20 seasons and over 450 episodes. "NCIS: Los Angeles" offers more action and espionage, while "NCIS: New Orleans" showcases the unique atmosphere of the Big Easy. "NCIS: Hawai'i" emphasizes teamwork and collaboration, and "NCIS: Sydney" takes the franchise global by teaming up with the Australian Federal Police. Fans are eager to see what other additions the "NCIS" universe has in store.