Sitcoms

Sitcoms have been on television for many decades, and most of them follow a very similar pattern with very similar characteristics. They typically have an episodic format, which basically means that each episode could stand alone. This is in contrast to a serial format, in which things carry over between episodes and there is a long term plot. Along with being episodic, sitcom characters often do not age, there is usually little character arc, and there is almost always a central question in each episode. These questions are usually introduced toward the beginning of each episode and not answered until the very end.
My favorite sitcom, and often considered the greatest of all time, is M*A*S*H, which ran 1972-1983. M*A*S*H followed a group of doctors and nurses stationed at the 4077th Mobile Army Surgical Hospital in South Korea during the Korean War, and like most sitcoms, it followed the episodic format. The show extended the three year Korean War to an eleven season show. The characters do not really age, nor do they develop and grow. Each character stayed essentially the same throughout their time on the show. Also, each episode contained a central theme or lesson, most of which had to do with the horrors of war and stupidity of the army.
For instance, "5 O'Clock Charlie", which was the 2nd episode of the 2nd season, is about a North Korean bomber pilot attempting to bomb an ammo depot near the MASH unit. The bomber, cleverly dubbed 5 O'Clock Charlie, throws a bomb at the depot from his plane everday at 5:00 pm, and misses everytime. The doctors and nurses find this very amusing, and even begin betting on how badly Charlie will miss the depot. Frank Burns, the show's antagonist, finds Charlie to be a serious threat, and request an anti-aircraft gun. Hawkeye, the show's protagonist, argues that the gun will just attract more attacks on the MASH unit. Despite Hawkeye's concerns, the anti-aircraft gun is installed. On Charlie's next attack, the gun is prepared to shoot him down, but Hawkeye confuses the gunners and has them aim and destroy the ammo depot. This ends Charlie's attacks and removes the gun from the hospital. The episode is a comment on the stupidity of the army. The reason the attacks happened in the first place was the army's "brilliant" idea of putting an ammo depot at a hospital, and then they decided to arm the hospital, provoking more attacks.